From 70e7bda87e6516283be72505bfbd897625059c12 Mon Sep 17 00:00:00 2001
From: Nils Schneider <nils.schneider@posteo.de>
Date: Mon, 24 Nov 2025 23:44:35 +0100
Subject: [PATCH] refactor: introduce dedicated identifier types for improved
 clarity and type safety

---
 frontend/src/app/DocumentsRoute.tsx           |   3 +-
 frontend/src/app/LoginRoute.tsx               |  20 +-
 frontend/src/app/UploadQueueOverlay.tsx       |   8 +-
 frontend/src/app/entryKey.ts                  |   6 +-
 frontend/src/app/useDetailPanel.ts            |  10 +-
 frontend/src/app/useDocumentPreview.ts        |   4 +-
 frontend/src/app/useDocumentSelection.ts      |  13 +-
 frontend/src/app/useDocumentsSearch.ts        |   3 +-
 frontend/src/app/useManagementModals.tsx      |   4 +-
 frontend/src/app/useWorkspaceSelection.ts     |   8 +-
 frontend/src/app/useWorkspaceSurface.tsx      |   3 +-
 frontend/src/asset_manager.ts                 |   2 +-
 .../correspondents/CorrespondentsPanel.tsx    |  10 +-
 frontend/src/desktop/DesktopDocumentCard.tsx  |  17 +-
 frontend/src/desktop/DesktopPreviewCard.tsx   |   5 +-
 frontend/src/desktop/DesktopWorkspace.tsx     |  15 +-
 frontend/src/desktop/db.ts                    |  36 +-
 .../src/desktop/hooks/usePreviewMetadata.ts   |   9 +-
 frontend/src/desktop/pointer/pointerUtils.ts  |   7 +-
 frontend/src/desktop/useDocumentDrag.ts       | 357 +++++-----
 frontend/src/desktop/workspaceEngine.ts       |  65 +-
 frontend/src/detail/PreviewZoomOverlay.tsx    |  66 +-
 frontend/src/detail/useDetailWorkspace.ts     |   3 +-
 frontend/src/documents/CorrespondentLinks.tsx |   8 +-
 frontend/src/documents/DocumentInfoPanel.tsx  |  12 +-
 .../src/documents/DocumentSummarySection.tsx  |  13 +-
 .../src/documents/DocumentThumbnailImage.tsx  |   2 +-
 frontend/src/documents/DocumentsGrid.tsx      | 639 +++++++++--------
 frontend/src/documents/DocumentsList.tsx      | 673 +++++++++---------
 frontend/src/documents/DocumentsManager.ts    |   3 +-
 .../src/documents/SelectionAssignmentMenu.tsx |  12 +-
 .../documents/SelectionFloatingActions.tsx    |   8 +-
 .../context/DocumentsFilterContext.tsx        |   5 +-
 frontend/src/documents/correspondents.ts      |   8 +-
 .../documents/hooks/useBulkDocumentActions.ts | 143 ++--
 .../documents/hooks/useDocumentsPanelProps.ts |   7 +-
 .../documents/hooks/useDocumentsSelection.ts  |  25 +-
 .../src/documents/panel/DocumentsPanel.tsx    |  12 +-
 .../documents/panel/DocumentsPanelHeader.tsx  |  15 +-
 frontend/src/documents/tagTransfer.ts         |  21 +-
 frontend/src/documents/useEntryPointer.ts     |   6 +-
 frontend/src/documents/useInlineRename.ts     |  16 +-
 frontend/src/folders/FolderManagerContext.tsx |   2 +-
 .../src/hooks/documents/useCorrespondents.ts  |   8 +-
 .../useDocumentCorrespondentActions.ts        |   7 +-
 .../documents/useDocumentDragHandlers.ts      |   6 +-
 .../hooks/documents/useDocumentMutations.ts   |   4 +-
 .../src/hooks/documents/useDocumentTagging.ts |  95 ++-
 .../src/hooks/documents/useDocumentUploads.ts |   2 +-
 frontend/src/hooks/documents/useDocuments.ts  |   3 +-
 .../hooks/documents/useDocumentsWorkspace.ts  |   5 +-
 frontend/src/hooks/documents/useFileDrop.ts   |   2 +-
 frontend/src/hooks/documents/useFolderTree.ts |  18 +-
 .../hooks/documents/useFolderTreeActions.ts   |   2 +-
 frontend/src/hooks/documents/useTags.ts       |  11 +-
 .../src/hooks/documents/useTenantManager.ts   |   9 +-
 .../documents/useWorkspaceBreadcrumbs.ts      |   4 +-
 .../hooks/documents/useWorkspaceDeskProps.ts  |   9 +-
 .../documents/useWorkspaceSelectionSync.ts    |   9 +-
 .../hooks/documents/useWorkspaceTaxonomies.ts |   3 +-
 frontend/src/hooks/useAssetNavigator.ts       |   7 +-
 frontend/src/lib/apiTypes.ts                  |   3 +-
 frontend/src/login/LoginView.tsx              | 154 ++--
 frontend/src/preview/DocumentViewerLayout.tsx |  16 +-
 frontend/src/preview/DocumentViewerPanel.tsx  |  19 +-
 frontend/src/routes/DocumentViewerRoute.tsx   |   3 +-
 .../components/CapabilityDropdown.tsx         |   4 +-
 .../settings/sections/ApiTokensSection.tsx    |  33 +-
 .../sections/CapabilitySetsSection.tsx        |   5 +-
 .../src/settings/sections/PasskeysSection.tsx |   4 +-
 frontend/src/settings/useApiTokens.ts         |  21 +-
 frontend/src/settings/useCapabilitySets.ts    |   3 +-
 frontend/src/settings/usePasskeys.ts          |  11 +-
 frontend/src/sidebar/Sidebar.tsx              | 319 +++++----
 frontend/src/sidebar/useSidebarProps.ts       |   3 +-
 frontend/src/types/identifiers.ts             |  11 +
 frontend/src/ui/QuickAddMenu.tsx              |   6 +-
 frontend/src/utils/date.ts                    |  12 +-
 frontend/src/utils/ocr.ts                     |   4 +-
 79 files changed, 1567 insertions(+), 1572 deletions(-)
 create mode 100644 frontend/src/types/identifiers.ts

diff --git a/frontend/src/app/DocumentsRoute.tsx b/frontend/src/app/DocumentsRoute.tsx
index aa47378..0142b62 100644
--- a/frontend/src/app/DocumentsRoute.tsx
+++ b/frontend/src/app/DocumentsRoute.tsx
@@ -11,8 +11,7 @@ import { DocumentsHeaderBreadcrumb } from '../documents/panel/DocumentsPanelHead
 import { SidebarProvider, useSidebarContext } from '../sidebar/SidebarContext';
 import { PanelManagerProvider, usePanelManager } from './PanelManagerContext';
 import Sidebar from '../sidebar/Sidebar';
-
-type Identifier = string | number;
+import type { Identifier } from '../types/identifiers';
 
 type EnsureAssetUrl = (
   docId: Identifier,
diff --git a/frontend/src/app/LoginRoute.tsx b/frontend/src/app/LoginRoute.tsx
index 1915506..7f63101 100644
--- a/frontend/src/app/LoginRoute.tsx
+++ b/frontend/src/app/LoginRoute.tsx
@@ -28,7 +28,7 @@ interface StatusMessage {
 }
 
 interface TenantOption {
-  id?: string | number | null;
+  id?: string | null;
   name?: string | null;
 }
 
@@ -321,7 +321,7 @@ const LoginRoute: React.FC = () => {
         const payload: {
           magic_token: string;
           username?: string;
-          preferred_tenant_id?: string | number;
+          preferred_tenant_id?: string;
         } = {
           magic_token: magicToken,
         };
@@ -520,14 +520,14 @@ const LoginRoute: React.FC = () => {
         onCancelSelection={handleCancelSelection}
         selectingTenantId={selectingTenantId}
         onPasskeyLogin={handlePasskeyLogin}
-      passkeySupported={passkeySupported}
-      passkeyLoading={passkeyLoading}
-      onSignup={handleSignup}
-      signupSupported={signupSupported}
-      signupLoading={signupLoading}
-      magicLoginPending={magicLoginPending}
-      initialUsername={magicLoginParams.username || ''}
-    />
+        passkeySupported={passkeySupported}
+        passkeyLoading={passkeyLoading}
+        onSignup={handleSignup}
+        signupSupported={signupSupported}
+        signupLoading={signupLoading}
+        magicLoginPending={magicLoginPending}
+        initialUsername={magicLoginParams.username || ''}
+      />
     </div>
   );
 };
diff --git a/frontend/src/app/UploadQueueOverlay.tsx b/frontend/src/app/UploadQueueOverlay.tsx
index 98052e1..180f253 100644
--- a/frontend/src/app/UploadQueueOverlay.tsx
+++ b/frontend/src/app/UploadQueueOverlay.tsx
@@ -15,12 +15,12 @@ import PanelHeader from '../ui/PanelHeader';
 type UploadStatus = 'pending' | 'uploading' | 'success' | 'duplicate' | 'error' | (string & {});
 
 interface UploadQueueItem {
-  id: string | number;
+  id: string;
   name: string;
   status: UploadStatus;
   error?: string | null;
-  document?: { id?: string | number; title?: string };
-  conflictDocumentId?: string | number;
+  document?: { id?: string; title?: string };
+  conflictDocumentId?: string;
 }
 
 interface UploadQueueOverlayProps {
@@ -191,7 +191,7 @@ const UploadQueueOverlay = ({ queue = [], onClearQueue }: UploadQueueOverlayProp
                             {item.error}
                           </span>
                         ) : (
-                        <span>{meta.label}</span>
+                          <span>{meta.label}</span>
                         )}
                       </div>
                     </div>
diff --git a/frontend/src/app/entryKey.ts b/frontend/src/app/entryKey.ts
index 55bfbf6..a95d0ad 100644
--- a/frontend/src/app/entryKey.ts
+++ b/frontend/src/app/entryKey.ts
@@ -1,13 +1,15 @@
+import type { DocumentId, FolderId } from '../types/identifiers';
+
 // Entry key utilities for workspace selection
 // Entry keys are strings in the format "document:id" or "folder:id"
 
 const ENTRY_KEY_SEPARATOR = ':';
 
 // Create entry key strings
-export const createDocumentEntryKey = (documentId: string | number): string =>
+export const createDocumentEntryKey = (documentId: DocumentId): string =>
     `document${ENTRY_KEY_SEPARATOR}${documentId}`;
 
-export const createFolderEntryKey = (folderId: string | number): string =>
+export const createFolderEntryKey = (folderId: FolderId): string =>
     `folder${ENTRY_KEY_SEPARATOR}${folderId}`;
 
 // Type guards for entry key strings
diff --git a/frontend/src/app/useDetailPanel.ts b/frontend/src/app/useDetailPanel.ts
index 7ad3840..671e5d0 100644
--- a/frontend/src/app/useDetailPanel.ts
+++ b/frontend/src/app/useDetailPanel.ts
@@ -1,19 +1,19 @@
 import { useCallback, useEffect, useRef, useState } from 'react';
 
 export interface DetailDocument {
-  id?: string | number;
+  id?: string;
   [key: string]: unknown;
 }
 
 interface UseDetailPanelOptions {
-  documentLookup: Map<string | number, DetailDocument>;
+  documentLookup: Map<string, DetailDocument>;
   orderedSelectedDocuments: DetailDocument[];
 }
 
 interface OpenDetailPanelArgs {
-  documentId?: string | number;
+  documentId?: string;
   document?: DetailDocument | null;
-  documentIds?: Array<string | number>;
+  documentIds?: Array<string>;
   documents?: DetailDocument[];
 }
 
@@ -22,7 +22,7 @@ export const useDetailPanel = ({
   orderedSelectedDocuments,
 }: UseDetailPanelOptions) => {
   const [detailPanelOpen, setDetailPanelOpen] = useState(false);
-  const [detailPanelDocId, setDetailPanelDocId] = useState<string | number | null>(null);
+  const [detailPanelDocId, setDetailPanelDocId] = useState<string | null>(null);
   const [detailPanelDocument, setDetailPanelDocument] = useState<DetailDocument | null>(null);
   const latestOrderedDocsRef = useRef<DetailDocument[]>([]);
 
diff --git a/frontend/src/app/useDocumentPreview.ts b/frontend/src/app/useDocumentPreview.ts
index 1048bb4..ccbd513 100644
--- a/frontend/src/app/useDocumentPreview.ts
+++ b/frontend/src/app/useDocumentPreview.ts
@@ -5,8 +5,8 @@ import type {
   SetStateAction,
 } from 'react';
 import { fetchDocument } from '../lib/apiClient';
+import type { DocumentId } from '../types/identifiers';
 
-type DocumentId = string | number;
 type FolderId = DocumentId | 'root';
 
 type DocumentLike = {
@@ -102,7 +102,7 @@ const useDocumentPreview = ({
     async (documentId: DocumentId, { force = false }: { force?: boolean } = {}): Promise<DocumentLink | null> => {
       if (!documentId) return null;
 
-    const existing = documentLinks.get(documentId);
+      const existing = documentLinks.get(documentId);
       const now = Date.now();
       const expiresAt = existing?.expiresAt ?? null;
       if (!force && existing && (!expiresAt || expiresAt > now)) {
diff --git a/frontend/src/app/useDocumentSelection.ts b/frontend/src/app/useDocumentSelection.ts
index 11f9285..6005fc8 100644
--- a/frontend/src/app/useDocumentSelection.ts
+++ b/frontend/src/app/useDocumentSelection.ts
@@ -6,8 +6,7 @@ import {
   isFolderEntry,
   getEntryId,
 } from './entryKey';
-
-type DocumentId = string | number;
+import type { DocumentId } from '../types/identifiers';
 
 interface SelectionEventLike {
   shiftKey?: boolean;
@@ -21,7 +20,7 @@ interface UseDocumentSelectionOptions {
 }
 
 interface ApplySelectionOptions {
-  anchor?: string;
+  anchor: string | null;
   interactedKeys?: string[];
 }
 
@@ -35,8 +34,8 @@ export const useDocumentSelection = ({
   const selectionOrderRef = useRef<string[]>(initialEntries);
   const selectionAnchorRef = useRef<string | null>(null);
   const selectionInitializedRef = useRef(false);
-  const [focusedDocumentId, setFocusedDocumentId] = useState<DocumentId | undefined>(undefined);
-  const [focusedRowKey, setFocusedRowKey] = useState<string | undefined>(undefined);
+  const [focusedDocumentId, setFocusedDocumentId] = useState<DocumentId | null>(null);
+  const [focusedRowKey, setFocusedRowKey] = useState<string | null>(null);
 
   const visibleRowKeySetRef = useRef<Set<string>>(new Set());
   const navigableRowKeysRef = useRef<string[]>([]);
@@ -90,7 +89,7 @@ export const useDocumentSelection = ({
   const applySelection = useCallback(
     (
       rowKeys: Array<string | null>,
-      { anchor, interactedKeys = [] }: ApplySelectionOptions = {},
+      { anchor = null, interactedKeys = [] }: ApplySelectionOptions = { anchor: null, interactedKeys: [] },
     ) => {
       const visibleRowKeySet = visibleRowKeySetRef.current;
       const unique: string[] = [];
@@ -117,7 +116,7 @@ export const useDocumentSelection = ({
         }
       });
 
-      let resolvedAnchor = anchor;
+      let resolvedAnchor: string | null = anchor ?? null;
       if (resolvedAnchor && !unique.includes(resolvedAnchor)) {
         resolvedAnchor = null;
       }
diff --git a/frontend/src/app/useDocumentsSearch.ts b/frontend/src/app/useDocumentsSearch.ts
index be2ad34..5e024e3 100644
--- a/frontend/src/app/useDocumentsSearch.ts
+++ b/frontend/src/app/useDocumentsSearch.ts
@@ -2,8 +2,7 @@ import { useCallback, useEffect, useMemo, useState } from 'react';
 import type { Dispatch, SetStateAction } from 'react';
 import { TAG_FILTER_UNTAGGED } from './workspaceUtils';
 import { listDocuments } from '../lib/apiClient';
-
-type Identifier = string | number;
+import type { Identifier } from '../types/identifiers';
 
 type DocumentLike = { id?: Identifier } & Record<string, unknown>;
 
diff --git a/frontend/src/app/useManagementModals.tsx b/frontend/src/app/useManagementModals.tsx
index 159dfda..8f44ca2 100644
--- a/frontend/src/app/useManagementModals.tsx
+++ b/frontend/src/app/useManagementModals.tsx
@@ -9,13 +9,13 @@ const TAGS_MODAL = 'tags';
 const CORRESPONDENTS_MODAL = 'correspondents';
 
 interface TagRecord {
-  id?: string | number;
+  id?: string;
   label?: string;
   [key: string]: unknown;
 }
 
 interface CorrespondentRecord {
-  id?: string | number;
+  id?: string;
   name?: string;
   [key: string]: unknown;
 }
diff --git a/frontend/src/app/useWorkspaceSelection.ts b/frontend/src/app/useWorkspaceSelection.ts
index d53a1e3..f6811f3 100644
--- a/frontend/src/app/useWorkspaceSelection.ts
+++ b/frontend/src/app/useWorkspaceSelection.ts
@@ -10,8 +10,8 @@ interface SelectionEntry {
 }
 
 interface WorkspaceSelectionOptions {
-  onDocumentActivate?: (id: string | number) => void;
-  onInspectFolder?: (id: string | number) => void;
+  onDocumentActivate?: (id: string) => void;
+  onInspectFolder?: (id: string) => void;
 }
 
 const identity = <T,>(value: T) => value;
@@ -71,7 +71,7 @@ export const useWorkspaceSelection = ({
   );
 
   const inspectDocument = useCallback(
-    (documentId?: string | number) => {
+    (documentId?: string) => {
       if (!documentId) return;
       onDocumentActivate(documentId);
     },
@@ -79,7 +79,7 @@ export const useWorkspaceSelection = ({
   );
 
   const inspectFolder = useCallback(
-    (folderId?: string | number) => {
+    (folderId?: string) => {
       if (!folderId) return;
       onInspectFolder(folderId);
     },
diff --git a/frontend/src/app/useWorkspaceSurface.tsx b/frontend/src/app/useWorkspaceSurface.tsx
index 1a97459..4b5a819 100644
--- a/frontend/src/app/useWorkspaceSurface.tsx
+++ b/frontend/src/app/useWorkspaceSurface.tsx
@@ -5,8 +5,7 @@ import DocumentsPanel from '../documents/panel/DocumentsPanel';
 import DocumentViewerPanel from '../preview/DocumentViewerPanel';
 import { usePanelManager } from './PanelManagerContext';
 import { FolderManagerProvider } from '../folders/FolderManagerContext';
-
-type Identifier = string | number;
+import type { Identifier } from '../types/identifiers';
 
 type EnsureAssetUrl = (docId: Identifier, asset: unknown, options?: Record<string, unknown>) => Promise<unknown> | void;
 type EnsurePreviewData = (docId: Identifier, options?: Record<string, unknown>) => Promise<unknown>;
diff --git a/frontend/src/asset_manager.ts b/frontend/src/asset_manager.ts
index 1b207be..5899fc1 100644
--- a/frontend/src/asset_manager.ts
+++ b/frontend/src/asset_manager.ts
@@ -1,4 +1,4 @@
-export type Identifier = string | number;
+import type { Identifier } from './types/identifiers';
 
 type Nullable<T> = T | null;
 
diff --git a/frontend/src/correspondents/CorrespondentsPanel.tsx b/frontend/src/correspondents/CorrespondentsPanel.tsx
index ef3f457..b8e8fa1 100644
--- a/frontend/src/correspondents/CorrespondentsPanel.tsx
+++ b/frontend/src/correspondents/CorrespondentsPanel.tsx
@@ -7,7 +7,7 @@ interface CorrespondentUsage {
 }
 
 export interface CorrespondentEntry {
-  id?: string | number;
+  id?: string;
   name?: string;
   usage?: CorrespondentUsage;
   [key: string]: unknown;
@@ -17,8 +17,8 @@ export interface CorrespondentsPanelProps {
   correspondents?: CorrespondentEntry[];
   onRefresh?: () => void | Promise<void>;
   onCreate: (payload: { name: string }) => Promise<CorrespondentEntry | void>;
-  onUpdate: (id: string | number, payload: { name: string }) => Promise<void>;
-  onDelete: (id: string | number) => Promise<void>;
+  onUpdate: (id: string, payload: { name: string }) => Promise<void>;
+  onDelete: (id: string) => Promise<void>;
   onNotify?: (message: string, variant?: string) => void;
 }
 
@@ -30,12 +30,12 @@ function CorrespondentsPanel({
   onDelete,
   onNotify,
 }: CorrespondentsPanelProps) {
-  const [editingId, setEditingId] = useState<string | number | null>(null);
+  const [editingId, setEditingId] = useState<string | null>(null);
   const [draftName, setDraftName] = useState('');
   const [createName, setCreateName] = useState('');
   const [saving, setSaving] = useState(false);
   const [creating, setCreating] = useState(false);
-  const [deletingId, setDeletingId] = useState<string | number | null>(null);
+  const [deletingId, setDeletingId] = useState<string | null>(null);
 
   const startEdit = useCallback((correspondent: CorrespondentEntry) => {
     setEditingId(correspondent.id);
diff --git a/frontend/src/desktop/DesktopDocumentCard.tsx b/frontend/src/desktop/DesktopDocumentCard.tsx
index 9a1504b..25c01ae 100644
--- a/frontend/src/desktop/DesktopDocumentCard.tsx
+++ b/frontend/src/desktop/DesktopDocumentCard.tsx
@@ -3,17 +3,18 @@ import DesktopPreviewCard from './DesktopPreviewCard';
 import { resolveCorrespondents } from '../documents/correspondents';
 import { getTagColorStyle } from '../utils/colors';
 import { preventAll } from './events';
+import type { DocumentId } from '../types/identifiers';
 
 type DocumentLike = {
-  id?: string | number;
+  id?: string;
   title?: string;
-  tags?: Array<{ id?: string | number; label?: string; color?: string | null }>;
+  tags?: Array<{ id?: string; label?: string; color?: string | null }>;
   [key: string]: unknown;
 };
 
 interface PendingRemovalTag {
-  docId?: string | number;
-  tagId?: string | number;
+  docId?: string;
+  tagId?: string;
 }
 
 interface DesktopDocumentCardProps {
@@ -30,10 +31,10 @@ interface DesktopDocumentCardProps {
   getDocumentAsset?: (...args: any[]) => unknown;
   handleNavigatorSnapshot?: (...args: any[]) => void;
   cardPointerHandlers?: React.HTMLAttributes<HTMLDivElement>;
-  onDocumentActivate?: (id: string | number) => void;
-  onTagDragEnter?: (event: React.DragEvent<HTMLDivElement>, docId: string | number) => void;
-  onTagDragOver?: (event: React.DragEvent<HTMLDivElement>, docId: string | number) => void;
-  onTagDragLeave?: (event: React.DragEvent<HTMLDivElement>, docId: string | number) => void;
+  onDocumentActivate?: (id: string) => void;
+  onTagDragEnter?: (event: React.DragEvent<HTMLDivElement>, docId: DocumentId) => void;
+  onTagDragOver?: (event: React.DragEvent<HTMLDivElement>, docId: DocumentId) => void;
+  onTagDragLeave?: (event: React.DragEvent<HTMLDivElement>, docId: DocumentId) => void;
   onTagDrop?: (event: React.DragEvent<HTMLDivElement>, doc: DocumentLike) => void;
   onDocTagPointerDown?: (event: React.PointerEvent<HTMLElement>, doc: DocumentLike, tag: any) => void;
   onDocTagDragStart?: (event: React.DragEvent<HTMLElement>, doc: DocumentLike, tag: any) => void;
diff --git a/frontend/src/desktop/DesktopPreviewCard.tsx b/frontend/src/desktop/DesktopPreviewCard.tsx
index 12c1501..9f73ec8 100644
--- a/frontend/src/desktop/DesktopPreviewCard.tsx
+++ b/frontend/src/desktop/DesktopPreviewCard.tsx
@@ -1,8 +1,7 @@
 import { useEffect } from 'react';
 import type { JSX } from 'react';
 import { useAssetNavigator } from '../hooks/useAssetNavigator';
-
-type Identifier = string | number;
+import type { Identifier } from '../types/identifiers';
 
 interface DocumentLike {
   id?: Identifier;
@@ -21,7 +20,7 @@ interface AssetLike {
 type EnsureAssetUrl = (
   documentId: Identifier,
   asset: AssetLike,
-  options?: { force?: boolean; [key: string]: unknown },
+  options?: { force?: boolean;[key: string]: unknown },
 ) => Promise<unknown>;
 
 type GetDocumentAsset = (document: DocumentLike | null, assetType: string) => AssetLike | null;
diff --git a/frontend/src/desktop/DesktopWorkspace.tsx b/frontend/src/desktop/DesktopWorkspace.tsx
index 49b74b2..7a95b93 100644
--- a/frontend/src/desktop/DesktopWorkspace.tsx
+++ b/frontend/src/desktop/DesktopWorkspace.tsx
@@ -29,8 +29,7 @@ import '../styles/workspace/workspace-layout.css';
 import '../styles/workspace/workspace-items.css';
 import '../styles/workspace/workspace-cards.css';
 import { useWorkspaceSelectionContext } from '../app/WorkspaceSelectionContext';
-
-type Identifier = string | number;
+import type { DocumentId, Identifier } from '../types/identifiers';
 
 type TagLike = { id?: Identifier | null; label?: string; color?: string | null } | null;
 type DocumentLinkLike = { url?: string | null; mimeType?: string | null };
@@ -79,7 +78,7 @@ interface DocumentSizeInfo {
 }
 
 interface PreviewMetadataEntry {
-  docId: string;
+  docId: DocumentId;
   width: number;
   height: number;
 }
@@ -225,7 +224,7 @@ const DesktopWorkspace: React.FC<DesktopWorkspaceProps> = ({
       const syntheticEvent = event || ({
         metaKey: true,
         ctrlKey: true,
-        preventDefault: () => {},
+        preventDefault: () => { },
       } as unknown as PointerEvent);
       docIds.forEach((id) => {
         const key = getDocRowKey(id);
@@ -354,7 +353,7 @@ const DesktopWorkspace: React.FC<DesktopWorkspaceProps> = ({
     engine.recalcVisibleDocIds();
   }, [engine]);
 
-  const setDraggingId = useCallback((value: string | number | null) => {
+  const setDraggingId = useCallback((value: string | null) => {
     engine.setDraggingId(value);
   }, [engine]);
 
@@ -686,7 +685,7 @@ const DesktopWorkspace: React.FC<DesktopWorkspaceProps> = ({
     },
     [resolvePreviewDimensions],
   );
- 
+
 
   useEffect(() => {
     if (draggingId && !items.some((doc) => String(doc.id) === draggingId)) {
@@ -1072,8 +1071,8 @@ function DesktopWorkspaceView({
               const dragging = docKey ? draggingId === docKey : false;
               const docTagKeys = Array.isArray(doc?.tags)
                 ? doc.tags
-                    .map((tag) => (tag?.id != null ? String(tag.id) : null))
-                    .filter((id): id is string => Boolean(id))
+                  .map((tag) => (tag?.id != null ? String(tag.id) : null))
+                  .filter((id): id is string => Boolean(id))
                 : [];
               const matchesFilter =
                 activeTagSet.size === 0 || docTagKeys.some((key) => activeTagSet.has(key));
diff --git a/frontend/src/desktop/db.ts b/frontend/src/desktop/db.ts
index 85ca546..d4c3116 100644
--- a/frontend/src/desktop/db.ts
+++ b/frontend/src/desktop/db.ts
@@ -1,3 +1,6 @@
+import type { DocumentId } from '../types/identifiers';
+type TenantId = import('../types/identifiers').TenantId;
+
 const DB_NAME = 'papercrate_desk';
 const DB_VERSION = 1;
 const LAYOUT_STORE = 'layouts';
@@ -107,9 +110,9 @@ const withStore = async <T>(mode: TransactionMode, handler: (store: IDBObjectSto
 };
 
 interface LayoutRecord {
-  tenantId: string | number;
-  viewId: string | number;
-  documentId: string | number;
+  tenantId: TenantId;
+  viewId: string;
+  documentId: DocumentId;
   centerX?: number;
   centerY?: number;
   rotation?: number;
@@ -117,7 +120,13 @@ interface LayoutRecord {
   updatedAt?: number;
 }
 
-export const fetchLayoutRecords = async ({ tenantId, viewId }: { tenantId?: string | number; viewId?: string | number }): Promise<LayoutRecord[]> => {
+export const fetchLayoutRecords = async ({
+  tenantId,
+  viewId,
+}: {
+  tenantId?: TenantId;
+  viewId?: string;
+}): Promise<LayoutRecord[]> => {
   if (!tenantId || !viewId) {
     return [];
   }
@@ -133,7 +142,22 @@ export const fetchLayoutRecords = async ({ tenantId, viewId }: { tenantId?: stri
   }
 };
 
-export const upsertLayoutRecords = async ({ tenantId, viewId, entries }: { tenantId?: string | number; viewId?: string | number; entries?: Array<{ documentId?: string | number; centerX?: number; centerY?: number; rotation?: number; zIndex?: number; updatedAt?: number }> }) => {
+export const upsertLayoutRecords = async ({
+  tenantId,
+  viewId,
+  entries,
+}: {
+  tenantId?: TenantId;
+  viewId?: string;
+  entries?: Array<{
+    documentId?: DocumentId;
+    centerX?: number;
+    centerY?: number;
+    rotation?: number;
+    zIndex?: number;
+    updatedAt?: number;
+  }>;
+}) => {
   if (!tenantId || !viewId || !Array.isArray(entries) || !entries.length) {
     return;
   }
@@ -162,7 +186,7 @@ export const upsertLayoutRecords = async ({ tenantId, viewId, entries }: { tenan
   }
 };
 
-export const deleteTenantLayouts = async (tenantId?: string | number) => {
+export const deleteTenantLayouts = async (tenantId?: TenantId) => {
   if (!tenantId) {
     return;
   }
diff --git a/frontend/src/desktop/hooks/usePreviewMetadata.ts b/frontend/src/desktop/hooks/usePreviewMetadata.ts
index cbb9023..8dd63e5 100644
--- a/frontend/src/desktop/hooks/usePreviewMetadata.ts
+++ b/frontend/src/desktop/hooks/usePreviewMetadata.ts
@@ -1,23 +1,24 @@
 import { useEffect, useState } from 'react';
+import type { DocumentId } from '../../types/identifiers';
 interface DocumentLike {
-  id?: string | number;
+  id?: string;
   current_version?: unknown;
   tags?: unknown;
 }
 
 interface AssetLike {
-  id?: string | number;
+  id?: string;
   [key: string]: unknown;
 }
 
 interface PreviewMetadataEntry {
-  docId: string;
+  docId: DocumentId;
   width: number;
   height: number;
 }
 
 type GetDocumentAsset = (doc: DocumentLike, type: string) => AssetLike | null;
-type EnsureAssetUrl = (docId: string | number, asset: AssetLike, options?: { force?: boolean }) => Promise<AssetLike | null>;
+type EnsureAssetUrl = (docId: DocumentId, asset: AssetLike, options?: { force?: boolean }) => Promise<AssetLike | null>;
 
 const usePreviewMetadata = (
   documents: DocumentLike[] | null,
diff --git a/frontend/src/desktop/pointer/pointerUtils.ts b/frontend/src/desktop/pointer/pointerUtils.ts
index ef4e7de..0d1e99f 100644
--- a/frontend/src/desktop/pointer/pointerUtils.ts
+++ b/frontend/src/desktop/pointer/pointerUtils.ts
@@ -1,4 +1,5 @@
 import { safeInvoke } from '../events';
+import type { DocumentId } from '../../types/identifiers';
 
 export const CLICK_ACTIONS = {
   selectSingle: 'selectSingle',
@@ -25,9 +26,9 @@ export const LONG_PRESS_DURATION_MS = 450;
 export const withinThreshold = (dx: number, dy: number, thresholdSquared: number): boolean => (dx * dx + dy * dy) <= thresholdSquared;
 
 interface PointerIntentArgs {
-  doc: { id: string | number };
+  doc: { id: string };
   entryDescriptor: unknown;
-  selectedDocumentIds: Array<string | number>;
+  selectedDocumentIds: Array<string>;
   metaKey: boolean;
   pointerButton?: number;
   pointerType?: string;
@@ -35,7 +36,7 @@ interface PointerIntentArgs {
 }
 
 export interface PointerIntent {
-  docId: string | number;
+  docId: DocumentId;
   entryDescriptor: unknown;
   pointerType?: string;
   pointerButton?: number;
diff --git a/frontend/src/desktop/useDocumentDrag.ts b/frontend/src/desktop/useDocumentDrag.ts
index a237e40..cae7c07 100644
--- a/frontend/src/desktop/useDocumentDrag.ts
+++ b/frontend/src/desktop/useDocumentDrag.ts
@@ -19,8 +19,7 @@ import {
   applyDomTransform,
   type WorkspaceEngine,
 } from './workspaceEngine';
-
-type Identifier = string | number;
+import type { DocumentId, Identifier } from '../types/identifiers';
 
 interface DocumentLike {
   id?: Identifier | null;
@@ -121,7 +120,7 @@ interface UseDocumentDragOptions {
 type EngineInertiaState = Parameters<WorkspaceEngine['startInertiaAnimation']>[1];
 
 interface DragStateInternal extends EngineDragState {
-  docId: string;
+  docId: DocumentId;
   docKey: string;
   pointerId: number;
   originCenterX: number;
@@ -208,15 +207,15 @@ const useDocumentDrag = (options: UseDocumentDragOptions) => {
     bringToFront,
     setDraggingId,
     canvasSize,
-  openOverlayForDoc,
-  recalcVisibleDocIds,
-  settings,
-  containerRef: providedContainerRef,
-  onDocumentActivate,
-  onDocumentStackSelect,
-  selectedDocumentIds = [],
-  markLayoutDirty,
-} = options;
+    openOverlayForDoc,
+    recalcVisibleDocIds,
+    settings,
+    containerRef: providedContainerRef,
+    onDocumentActivate,
+    onDocumentStackSelect,
+    selectedDocumentIds = [],
+    markLayoutDirty,
+  } = options;
 
   const fallbackContainerRef = useRef<HTMLElement | null>(null);
   const containerRef = providedContainerRef ?? fallbackContainerRef;
@@ -237,7 +236,7 @@ const useDocumentDrag = (options: UseDocumentDragOptions) => {
 
   const tapHandler = usePointerTap<DragTapMetadata>({
     delay: 220,
-    onSingle: () => {},
+    onSingle: () => { },
     onDouble: ({ data, event }) => {
       if (!data?.docId) {
         return;
@@ -281,8 +280,8 @@ const useDocumentDrag = (options: UseDocumentDragOptions) => {
     }
     const keys = Array.isArray(docIds) && docIds.length
       ? docIds
-          .map((id) => (id != null ? String(id) : null))
-          .filter((value): value is string => Boolean(value))
+        .map((id) => (id != null ? String(id) : null))
+        .filter((value): value is string => Boolean(value))
       : Array.from(map.keys());
     keys.forEach((key) => {
       const transform = map.get(key);
@@ -350,8 +349,8 @@ const useDocumentDrag = (options: UseDocumentDragOptions) => {
       const stackDocIdsOptionRaw = options?.stackDocIds;
       const stackDocIdsOption = Array.isArray(stackDocIdsOptionRaw)
         ? stackDocIdsOptionRaw
-            .map((value) => (value != null ? String(value) : null))
-            .filter((value): value is string => Boolean(value))
+          .map((value) => (value != null ? String(value) : null))
+          .filter((value): value is string => Boolean(value))
         : null;
       const stackSelectionAppliedInitial = Boolean(options?.stackSelectionApplied);
       const wasSelectedAtPointerDown = Boolean(options?.wasSelected);
@@ -361,8 +360,8 @@ const useDocumentDrag = (options: UseDocumentDragOptions) => {
 
       let selectionIds: string[] = Array.isArray(selectedDocumentIds)
         ? selectedDocumentIds
-            .map((id) => (id != null ? String(id) : null))
-            .filter((id): id is string => Boolean(id))
+          .map((id) => (id != null ? String(id) : null))
+          .filter((id): id is string => Boolean(id))
         : [];
 
       if (!stackDocIdsOption && !pointerModifierActive && !wasSelectedAtPointerDown) {
@@ -399,7 +398,7 @@ const useDocumentDrag = (options: UseDocumentDragOptions) => {
       if (isGroupDrag) {
         selectionIds.forEach((id) => {
           if (id !== docKey) {
-        engine?.cancelInertiaAnimation?.(id);
+            engine?.cancelInertiaAnimation?.(id);
           }
         });
       }
@@ -491,7 +490,7 @@ const useDocumentDrag = (options: UseDocumentDragOptions) => {
           offsetY: baseOffsetY,
           targetRotation: initialRotation,
           displayRotation: initialRotation,
-          
+
         } satisfies DragGroupItemInternal;
       });
 
@@ -569,28 +568,28 @@ const useDocumentDrag = (options: UseDocumentDragOptions) => {
 
       setDraggingId(docKey);
 
-    if (isGroupDrag) {
-      groupItems.forEach((item) => {
-        if (item.docId === docKey) {
-          return;
-        }
-        const node = itemRefs.current.get(item.docId);
-        if (node) {
-          item.displayRotation = item.initialRotation;
-          const itemEntry = layoutRef.current.get(item.docId) || null;
-          applyDomTransform(node, {
-            centerX: item.currentCenterX,
-            centerY: item.currentCenterY,
-            width: item.width,
-            height: item.height,
-            rotation: item.displayRotation ?? 0,
-            scale: 1,
-            zIndex: itemEntry?.z,
-          });
-        }
-      });
-    }
-  }, [
+      if (isGroupDrag) {
+        groupItems.forEach((item) => {
+          if (item.docId === docKey) {
+            return;
+          }
+          const node = itemRefs.current.get(item.docId);
+          if (node) {
+            item.displayRotation = item.initialRotation;
+            const itemEntry = layoutRef.current.get(item.docId) || null;
+            applyDomTransform(node, {
+              centerX: item.currentCenterX,
+              centerY: item.currentCenterY,
+              width: item.width,
+              height: item.height,
+              rotation: item.displayRotation ?? 0,
+              scale: 1,
+              zIndex: itemEntry?.z,
+            });
+          }
+        });
+      }
+    }, [
     bringToFront,
     canvasPadding,
     containerRef,
@@ -674,147 +673,147 @@ const useDocumentDrag = (options: UseDocumentDragOptions) => {
         state.rotation = state.restRotation + state.dynamicRotation;
       };
 
-    if (state.isGroup) {
-      const containerRect = containerRef.current?.getBoundingClientRect?.();
-      if (containerRect) {
-        state.containerRectLeft = containerRect.left;
-        state.containerRectTop = containerRect.top;
-      }
-
-      const pointerCanvasX = event.clientX - state.containerRectLeft;
-      const pointerCanvasY = event.clientY - state.containerRectTop;
-      const deltaX = event.clientX - state.startX;
-      const deltaY = event.clientY - state.startY;
-
-      if (!state.moved) {
-        const distanceSquared = deltaX * deltaX + deltaY * deltaY;
-        if (distanceSquared < DRAG_HYSTERESIS_SQUARED) {
-          return;
+      if (state.isGroup) {
+        const containerRect = containerRef.current?.getBoundingClientRect?.();
+        if (containerRect) {
+          state.containerRectLeft = containerRect.left;
+          state.containerRectTop = containerRect.top;
         }
-        state.moved = true;
-        if (
-          !state.stackSelectionApplied
-          && Array.isArray(state.stackDocIds)
-          && state.stackDocIds.length > 0
-        ) {
-          safeInvoke(onDocumentStackSelect, state.stackDocIds as Identifier[], event, {
-            replace: state.stackReplace,
-          });
-          state.stackSelectionApplied = true;
-        }
-        if (!state.groupElevated) {
-          const layout = layoutRef.current;
-          const sortedGroup = state.activeDocIds
-            .filter((id) => id !== state.docKey)
-            .sort((a, b) => {
-              const aZ = layout.get(a)?.z ?? 0;
-              const bZ = layout.get(b)?.z ?? 0;
-              return aZ - bZ;
+
+        const pointerCanvasX = event.clientX - state.containerRectLeft;
+        const pointerCanvasY = event.clientY - state.containerRectTop;
+        const deltaX = event.clientX - state.startX;
+        const deltaY = event.clientY - state.startY;
+
+        if (!state.moved) {
+          const distanceSquared = deltaX * deltaX + deltaY * deltaY;
+          if (distanceSquared < DRAG_HYSTERESIS_SQUARED) {
+            return;
+          }
+          state.moved = true;
+          if (
+            !state.stackSelectionApplied
+            && Array.isArray(state.stackDocIds)
+            && state.stackDocIds.length > 0
+          ) {
+            safeInvoke(onDocumentStackSelect, state.stackDocIds as Identifier[], event, {
+              replace: state.stackReplace,
             });
+            state.stackSelectionApplied = true;
+          }
+          if (!state.groupElevated) {
+            const layout = layoutRef.current;
+            const sortedGroup = state.activeDocIds
+              .filter((id) => id !== state.docKey)
+              .sort((a, b) => {
+                const aZ = layout.get(a)?.z ?? 0;
+                const bZ = layout.get(b)?.z ?? 0;
+                return aZ - bZ;
+              });
 
-          sortedGroup.forEach((id) => bringToFront(id));
-          bringToFront(state.docKey);
-          state.groupElevated = true;
+            sortedGroup.forEach((id) => bringToFront(id));
+            bringToFront(state.docKey);
+            state.groupElevated = true;
+          }
         }
+
+        const docWidth = state.width;
+        const docHeight = state.height;
+        const halfWidth = docWidth / 2;
+        const halfHeight = docHeight / 2;
+        const canvasWidth = canvasSize.width || defaultCanvasWidth;
+        const canvasHeight = canvasSize.height || defaultCanvasHeight;
+        const minCenterX = canvasPadding + halfWidth;
+        const maxCenterX = Math.max(minCenterX, canvasWidth - canvasPadding - halfWidth);
+        const minCenterY = canvasPadding + halfHeight;
+        const maxCenterY = Math.max(minCenterY, canvasHeight - canvasPadding - halfHeight);
+
+        const desiredCenterX = pointerCanvasX - state.localPointerOffsetX;
+        const desiredCenterY = pointerCanvasY - state.localPointerOffsetY;
+        const centerX = clamp(desiredCenterX, minCenterX, maxCenterX);
+        const centerY = clamp(desiredCenterY, minCenterY, maxCenterY);
+
+        state.currentCenterX = centerX;
+        state.currentCenterY = centerY;
+
+        state.groupItems.forEach((item) => {
+          const isPrimary = item.docId === state.docKey;
+
+          if (isPrimary) {
+            item.currentCenterX = centerX;
+            item.currentCenterY = centerY;
+            item.offsetX = item.baseOffsetX ?? 0;
+            item.offsetY = item.baseOffsetY ?? 0;
+            item.displayRotation = state.rotation ?? item.displayRotation ?? 0;
+          } else {
+            const decay = 0.82;
+            const currentOffsetX = (item.offsetX ?? item.baseOffsetX ?? 0) * decay;
+            const currentOffsetY = (item.offsetY ?? item.baseOffsetY ?? 0) * decay;
+            item.offsetX = Math.abs(currentOffsetX) < 0.5 ? 0 : currentOffsetX;
+            item.offsetY = Math.abs(currentOffsetY) < 0.5 ? 0 : currentOffsetY;
+
+            const targetX = centerX + item.offsetX;
+            const targetY = centerY + item.offsetY;
+            const smoothing = 0.18;
+            item.currentCenterX += (targetX - item.currentCenterX) * smoothing;
+            item.currentCenterY += (targetY - item.currentCenterY) * smoothing;
+
+            const halfW = item.width / 2;
+            const halfH = item.height / 2;
+            const minX = canvasPadding + halfW;
+            const maxX = Math.max(minX, canvasWidth - canvasPadding - halfW);
+            const minY = canvasPadding + halfH;
+            const maxY = Math.max(minY, canvasHeight - canvasPadding - halfH);
+            item.currentCenterX = clamp(item.currentCenterX, minX, maxX);
+            item.currentCenterY = clamp(item.currentCenterY, minY, maxY);
+
+            const rotationBlend = 0.16;
+            item.displayRotation += (item.targetRotation - item.displayRotation) * rotationBlend;
+          }
+
+          const entry = layoutRef.current.get(item.docId) || null;
+          const payload = {
+            centerX: item.currentCenterX,
+            centerY: item.currentCenterY,
+            rotation: item.displayRotation ?? 0,
+            width: item.width,
+            height: item.height,
+            scale: isPrimary ? state.dragScale || 1 : 1,
+            zIndex: entry?.z,
+          };
+
+          setDragTransform(item.docId, payload);
+          const node = itemRefs.current.get(item.docId);
+          applyDomTransform(node, payload);
+        });
+
+        const currentTimestampGroup =
+          (Number.isFinite(event?.timeStamp))
+            ? event.timeStamp
+            : performance?.now
+              ? performance.now()
+              : Date.now();
+        const previousTimestampGroup = state.lastTimestamp ?? currentTimestampGroup;
+        let dtGroup = (currentTimestampGroup - previousTimestampGroup) / 1000;
+        if (!Number.isFinite(dtGroup) || dtGroup <= 0) {
+          dtGroup = MIN_TIMESTEP;
+        }
+        dtGroup = clamp(dtGroup, MIN_TIMESTEP, MAX_TIMESTEP);
+
+        state.lastClientX = event.clientX;
+        state.lastClientY = event.clientY;
+        state.lastTimestamp = currentTimestampGroup;
+
+        updatePointerAngularVelocity(pointerCanvasX, pointerCanvasY, centerX, centerY, dtGroup);
+        applyDynamicRotation(dtGroup, 0.96);
+        state.groupItems.forEach((item) => {
+          if (item.docId === state.docKey) {
+            item.displayRotation = state.rotation ?? item.displayRotation ?? 0;
+          }
+        });
+
+        return;
       }
-
-      const docWidth = state.width;
-      const docHeight = state.height;
-      const halfWidth = docWidth / 2;
-      const halfHeight = docHeight / 2;
-      const canvasWidth = canvasSize.width || defaultCanvasWidth;
-      const canvasHeight = canvasSize.height || defaultCanvasHeight;
-      const minCenterX = canvasPadding + halfWidth;
-      const maxCenterX = Math.max(minCenterX, canvasWidth - canvasPadding - halfWidth);
-      const minCenterY = canvasPadding + halfHeight;
-      const maxCenterY = Math.max(minCenterY, canvasHeight - canvasPadding - halfHeight);
-
-      const desiredCenterX = pointerCanvasX - state.localPointerOffsetX;
-      const desiredCenterY = pointerCanvasY - state.localPointerOffsetY;
-      const centerX = clamp(desiredCenterX, minCenterX, maxCenterX);
-      const centerY = clamp(desiredCenterY, minCenterY, maxCenterY);
-
-      state.currentCenterX = centerX;
-      state.currentCenterY = centerY;
-
-      state.groupItems.forEach((item) => {
-        const isPrimary = item.docId === state.docKey;
-
-        if (isPrimary) {
-          item.currentCenterX = centerX;
-          item.currentCenterY = centerY;
-          item.offsetX = item.baseOffsetX ?? 0;
-          item.offsetY = item.baseOffsetY ?? 0;
-          item.displayRotation = state.rotation ?? item.displayRotation ?? 0;
-        } else {
-          const decay = 0.82;
-          const currentOffsetX = (item.offsetX ?? item.baseOffsetX ?? 0) * decay;
-          const currentOffsetY = (item.offsetY ?? item.baseOffsetY ?? 0) * decay;
-          item.offsetX = Math.abs(currentOffsetX) < 0.5 ? 0 : currentOffsetX;
-          item.offsetY = Math.abs(currentOffsetY) < 0.5 ? 0 : currentOffsetY;
-
-          const targetX = centerX + item.offsetX;
-          const targetY = centerY + item.offsetY;
-          const smoothing = 0.18;
-          item.currentCenterX += (targetX - item.currentCenterX) * smoothing;
-          item.currentCenterY += (targetY - item.currentCenterY) * smoothing;
-
-          const halfW = item.width / 2;
-          const halfH = item.height / 2;
-          const minX = canvasPadding + halfW;
-          const maxX = Math.max(minX, canvasWidth - canvasPadding - halfW);
-          const minY = canvasPadding + halfH;
-          const maxY = Math.max(minY, canvasHeight - canvasPadding - halfH);
-          item.currentCenterX = clamp(item.currentCenterX, minX, maxX);
-          item.currentCenterY = clamp(item.currentCenterY, minY, maxY);
-
-          const rotationBlend = 0.16;
-          item.displayRotation += (item.targetRotation - item.displayRotation) * rotationBlend;
-        }
-
-        const entry = layoutRef.current.get(item.docId) || null;
-        const payload = {
-          centerX: item.currentCenterX,
-          centerY: item.currentCenterY,
-          rotation: item.displayRotation ?? 0,
-          width: item.width,
-          height: item.height,
-          scale: isPrimary ? state.dragScale || 1 : 1,
-          zIndex: entry?.z,
-        };
-
-        setDragTransform(item.docId, payload);
-        const node = itemRefs.current.get(item.docId);
-        applyDomTransform(node, payload);
-      });
-
-      const currentTimestampGroup =
-        (Number.isFinite(event?.timeStamp))
-          ? event.timeStamp
-          : performance?.now
-            ? performance.now()
-            : Date.now();
-      const previousTimestampGroup = state.lastTimestamp ?? currentTimestampGroup;
-      let dtGroup = (currentTimestampGroup - previousTimestampGroup) / 1000;
-      if (!Number.isFinite(dtGroup) || dtGroup <= 0) {
-        dtGroup = MIN_TIMESTEP;
-      }
-      dtGroup = clamp(dtGroup, MIN_TIMESTEP, MAX_TIMESTEP);
-
-      state.lastClientX = event.clientX;
-      state.lastClientY = event.clientY;
-      state.lastTimestamp = currentTimestampGroup;
-
-      updatePointerAngularVelocity(pointerCanvasX, pointerCanvasY, centerX, centerY, dtGroup);
-      applyDynamicRotation(dtGroup, 0.96);
-      state.groupItems.forEach((item) => {
-        if (item.docId === state.docKey) {
-          item.displayRotation = state.rotation ?? item.displayRotation ?? 0;
-        }
-      });
-
-      return;
-    }
       if (state.locked) {
         return;
       }
diff --git a/frontend/src/desktop/workspaceEngine.ts b/frontend/src/desktop/workspaceEngine.ts
index 4cf8e70..e3495d0 100644
--- a/frontend/src/desktop/workspaceEngine.ts
+++ b/frontend/src/desktop/workspaceEngine.ts
@@ -1,7 +1,7 @@
 import { clamp, formatTransform } from '../utils/math';
 import { fetchLayoutRecords, upsertLayoutRecords } from './db';
-
-type DocumentId = string;
+import type { DocumentId } from '../types/identifiers';
+type TenantId = import('../types/identifiers').TenantId;
 
 interface Point {
   x: number;
@@ -63,7 +63,7 @@ interface BaseMetrics {
 }
 
 interface DragGroupItem {
-  docId?: string | number | null;
+  docId?: string | null;
   width: number;
   height: number;
   currentCenterX?: number;
@@ -80,7 +80,7 @@ interface DragState {
 }
 
 interface InertiaSimulationState {
-  docId: string;
+  docId: DocumentId;
   restRotation: number;
   rotation: number;
   dynamicRotation: number;
@@ -106,7 +106,7 @@ interface WorkspaceSnapshot {
 
 type WorkspaceSubscriber = () => void;
 
-type DeskDocument = { id?: string | number | null } & Record<string, unknown>;
+type DeskDocument = { id?: string | null } & Record<string, unknown>;
 
 type EnsureDocumentSize = (doc: DeskDocument) => DocumentSize | null;
 
@@ -226,7 +226,7 @@ export const clampCardDimensions = (width: number, height: number): CardDimensio
   };
 };
 
-export const computeFallbackCardSize = (docId: string | number): CardDimensions | null => {
+export const computeFallbackCardSize = (docId: DocumentId): CardDimensions | null => {
   const baseSeed = seededRandom(`${docId}:fallback-size`);
   const aspectSeed = seededRandom(`${docId}:fallback-aspect`);
 
@@ -259,7 +259,7 @@ function randomRangeFromSeed(seedKey: string, min: number, max: number): number
   return min + seed * span;
 }
 
-function buildKey(docId: string | number, suffix: string): string {
+function buildKey(docId: DocumentId, suffix: string): string {
   return `${docId}::${suffix}`;
 }
 
@@ -525,63 +525,34 @@ const generateInitialLayout = (
 
 export class WorkspaceEngine {
   allowLayoutPersistence: boolean;
-
-  tenantId: string | null;
-
+  tenantId: TenantId | null;
   viewId: string | null;
-
   layout: Map<DocumentId, LayoutEntry>;
-
   layoutSnapshot: Map<DocumentId, LayoutEntry>;
-
   persistedLayout: Map<DocumentId, LayoutEntry>;
-
   layoutDirty: boolean;
-
   zCounter: number;
-
   canvasSize: { width: number; height: number };
-
   visibleDocIds: Set<DocumentId>;
-
   draggingId: string | null;
-
   tagDropTargetId: string | null;
-
   pendingTagDocId: string | null;
-
   pendingRemovalTag: unknown;
-
   dragInProgress: boolean;
-
   activeDragDocIds: Set<DocumentId>;
-
   pendingSnapshotSync: boolean;
-
   pendingPersistSync: boolean;
-
   persistDebounceId: number | null;
-
   items: DeskDocument[];
-
   documentLookup: Map<string, DeskDocument>;
-
   ensureDocumentSize: EnsureDocumentSize;
-
   resolveBaseMetrics: ResolveBaseMetrics;
-
   snapshotCache: WorkspaceSnapshot;
-
   subscribers: Set<WorkspaceSubscriber>;
-
   loadingPersisted: boolean;
-
   pendingPersistence: unknown;
-
   itemRefs: ItemRefs;
-
   inertiaAnimations: Map<string, InertiaSimulationState>;
-
   initialLoadDone: boolean;
 
   constructor({
@@ -716,7 +687,7 @@ export class WorkspaceEngine {
     this.emit();
   }
 
-  setDraggingId(docId: string | number | null): void {
+  setDraggingId(docId: DocumentId | null): void {
     const normalized = docId != null ? String(docId) : null;
     if (this.draggingId === normalized) {
       return;
@@ -725,7 +696,7 @@ export class WorkspaceEngine {
     this.emit();
   }
 
-  beginDrag(docIds: Array<string | number | null> = []): void {
+  beginDrag(docIds: Array<string | null> = []): void {
     this.dragInProgress = true;
     if (Array.isArray(docIds)) {
       this.activeDragDocIds = new Set(docIds.map((id) => (id != null ? String(id) : null)).filter(Boolean));
@@ -749,7 +720,7 @@ export class WorkspaceEngine {
     }
   }
 
-  setTagDropTargetId(docId: string | number | null): void {
+  setTagDropTargetId(docId: DocumentId | null): void {
     const normalized = docId != null ? String(docId) : null;
     if (this.tagDropTargetId === normalized) {
       return;
@@ -758,7 +729,7 @@ export class WorkspaceEngine {
     this.emit();
   }
 
-  setPendingTagDocId(docId: string | number | null): void {
+  setPendingTagDocId(docId: DocumentId | null): void {
     const normalized = docId != null ? String(docId) : null;
     if (this.pendingTagDocId === normalized) {
       return;
@@ -779,7 +750,7 @@ export class WorkspaceEngine {
     this.layoutDirty = true;
   }
 
-  getLayout(docId: string | number | null): LayoutEntry | null {
+  getLayout(docId: DocumentId | null): LayoutEntry | null {
     if (docId == null) {
       return null;
     }
@@ -788,7 +759,7 @@ export class WorkspaceEngine {
   }
 
   updateLayoutEntry(
-    docId: string | number | null,
+    docId: DocumentId | null,
     updater: (previous: LayoutEntry | null) => LayoutEntry | null,
   ): void {
     if (docId == null) {
@@ -807,7 +778,7 @@ export class WorkspaceEngine {
     this.persistLayoutSnapshot();
   }
 
-  bringToFront(docId: string | number | null): void {
+  bringToFront(docId: DocumentId | null): void {
     if (docId == null) {
       return;
     }
@@ -825,7 +796,7 @@ export class WorkspaceEngine {
   }
 
   applyTransform(
-    docId: string | number | null,
+    docId: DocumentId | null,
     centerX: number,
     centerY: number,
     width: number,
@@ -896,7 +867,7 @@ export class WorkspaceEngine {
     this.persistLayoutSnapshot();
   }
 
-  cancelInertiaAnimation(docId: string | number | null): void {
+  cancelInertiaAnimation(docId: DocumentId | null): void {
     const key = docId != null ? String(docId) : null;
     if (!key) {
       return;
@@ -995,7 +966,7 @@ export class WorkspaceEngine {
     return isSettled;
   }
 
-  startInertiaAnimation(docId: string | number | null, baseState: InertiaSimulationState): void {
+  startInertiaAnimation(docId: DocumentId | null, baseState: InertiaSimulationState): void {
     const raf = window.requestAnimationFrame;
     if (!raf) {
       return;
diff --git a/frontend/src/detail/PreviewZoomOverlay.tsx b/frontend/src/detail/PreviewZoomOverlay.tsx
index e095ca4..7cc477a 100644
--- a/frontend/src/detail/PreviewZoomOverlay.tsx
+++ b/frontend/src/detail/PreviewZoomOverlay.tsx
@@ -4,7 +4,7 @@ import { clamp } from '../utils/math';
 import PdfViewer from '../preview/PdfViewer';
 
 type DocumentLike = {
-  id?: string | number;
+  id?: string;
   title?: string;
   mime_type?: string | null;
   [key: string]: unknown;
@@ -43,7 +43,7 @@ const determineDisplayKind = (entry?: DocumentLink | null): DisplayKind => {
   return 'image';
 };
 
-const noop = () => {};
+const noop = () => { };
 
 const PreviewZoomOverlay: React.FC<PreviewZoomOverlayProps> = ({
   open = false,
@@ -214,22 +214,22 @@ const PreviewZoomOverlay: React.FC<PreviewZoomOverlayProps> = ({
     const key = event.key;
 
     if (key === ' ' || key === 'Space' || key === 'Spacebar') {
-    const target = event.target;
-    if (target instanceof HTMLElement) {
-      const tag = target.tagName ? target.tagName.toLowerCase() : '';
-      if (
-        target.isContentEditable
-        || tag === 'input'
-        || tag === 'textarea'
-        || tag === 'select'
-      ) {
-        return;
+      const target = event.target;
+      if (target instanceof HTMLElement) {
+        const tag = target.tagName ? target.tagName.toLowerCase() : '';
+        if (
+          target.isContentEditable
+          || tag === 'input'
+          || tag === 'textarea'
+          || tag === 'select'
+        ) {
+          return;
+        }
       }
+      event.preventDefault();
+      onClose();
+      return;
     }
-    event.preventDefault();
-    onClose();
-    return;
-  }
 
     if (key === 'Escape') {
       event.preventDefault();
@@ -291,19 +291,19 @@ const PreviewZoomOverlay: React.FC<PreviewZoomOverlayProps> = ({
 
   const contentStyle: CSSProperties = isNativeScale
     ? {
-        cursor: 'zoom-out',
-        width: naturalSize.width ? `${naturalSize.width}px` : 'auto',
-        height: naturalSize.height ? `${naturalSize.height}px` : 'auto',
-        maxWidth: 'none',
-        maxHeight: 'none',
-        touchAction: 'manipulation',
-      }
+      cursor: 'zoom-out',
+      width: naturalSize.width ? `${naturalSize.width}px` : 'auto',
+      height: naturalSize.height ? `${naturalSize.height}px` : 'auto',
+      maxWidth: 'none',
+      maxHeight: 'none',
+      touchAction: 'manipulation',
+    }
     : {
-        cursor: 'zoom-in',
-        maxWidth: '95vw',
-        maxHeight: '95vh',
-        touchAction: 'manipulation',
-      };
+      cursor: 'zoom-in',
+      maxWidth: '95vw',
+      maxHeight: '95vh',
+      touchAction: 'manipulation',
+    };
 
   if (!shouldRender) {
     return null;
@@ -323,11 +323,11 @@ const PreviewZoomOverlay: React.FC<PreviewZoomOverlayProps> = ({
       >
         <div
           className={stageClassName}
-        onClick={(event) => {
-          if (event.target === event.currentTarget) {
-            onClose();
-          }
-        }}
+          onClick={(event) => {
+            if (event.target === event.currentTarget) {
+              onClose();
+            }
+          }}
         >
           <div
             className={containerClassName}
diff --git a/frontend/src/detail/useDetailWorkspace.ts b/frontend/src/detail/useDetailWorkspace.ts
index 3693636..893df98 100644
--- a/frontend/src/detail/useDetailWorkspace.ts
+++ b/frontend/src/detail/useDetailWorkspace.ts
@@ -6,8 +6,7 @@ import { DEFAULT_FOLDER_NAME } from '../app/workspaceUtils';
 import { getEntryId, isDocumentEntry } from '../app/entryKey';
 import type { DocumentInfoPanelProps } from '../documents/DocumentInfoPanel';
 import type { EnsureAssetUrl, GetDocumentAsset } from '../utils/ocr';
-
-type Identifier = string | number;
+import type { Identifier } from '../types/identifiers';
 
 interface DocumentLike {
   id?: Identifier;
diff --git a/frontend/src/documents/CorrespondentLinks.tsx b/frontend/src/documents/CorrespondentLinks.tsx
index fdba8e4..ff717de 100644
--- a/frontend/src/documents/CorrespondentLinks.tsx
+++ b/frontend/src/documents/CorrespondentLinks.tsx
@@ -3,15 +3,15 @@ import React from 'react';
 const NBSP = String.fromCharCode(160);
 
 export interface CorrespondentLinkEntry {
-  id?: string | number | null;
+  id?: string | null;
   name?: string | null;
   key?: string;
 }
 
 interface CorrespondentLinksProps {
   correspondents?: CorrespondentLinkEntry[];
-  activeCorrespondentIdSet?: Set<string | number>;
-  onCorrespondentClick?: (id: string | number) => void;
+  activeCorrespondentIdSet?: Set<string>;
+  onCorrespondentClick?: (id: string) => void;
 }
 
 const CorrespondentLinks: React.FC<CorrespondentLinksProps> = ({
@@ -23,7 +23,7 @@ const CorrespondentLinks: React.FC<CorrespondentLinksProps> = ({
     return null;
   }
 
-  const activeSet = activeCorrespondentIdSet || new Set<string | number>();
+  const activeSet = activeCorrespondentIdSet || new Set<string>();
   const handleClick = (event: React.MouseEvent<HTMLButtonElement> | React.KeyboardEvent<HTMLButtonElement>, correspondent: CorrespondentLinkEntry) => {
     if (!onCorrespondentClick || correspondent.id == null) {
       return;
diff --git a/frontend/src/documents/DocumentInfoPanel.tsx b/frontend/src/documents/DocumentInfoPanel.tsx
index 7acfa1b..21e6257 100644
--- a/frontend/src/documents/DocumentInfoPanel.tsx
+++ b/frontend/src/documents/DocumentInfoPanel.tsx
@@ -36,7 +36,7 @@ export interface DocumentInfoPanelProps {
   activeTab?: string;
   onTabChange?: (tabId: string) => void;
   defaultTabId?: string;
-  resetKey?: string | number | null;
+  resetKey?: string | null;
   classNamePrefix?: string;
   hideTabNavWhenSingle?: boolean;
   summaryPlacement?: 'inline' | 'tabs';
@@ -204,11 +204,11 @@ const DocumentInfoPanel: React.FC<DocumentInfoPanelProps> = ({
 
   const summaryNode = summaryInline
     ? (
-        <>
-          {renderSummarySection()}
-          {renderDetailsSection()}
-        </>
-      )
+      <>
+        {renderSummarySection()}
+        {renderDetailsSection()}
+      </>
+    )
     : null;
 
   const visibleTabs = useMemo(() => {
diff --git a/frontend/src/documents/DocumentSummarySection.tsx b/frontend/src/documents/DocumentSummarySection.tsx
index 03b1b0c..8605740 100644
--- a/frontend/src/documents/DocumentSummarySection.tsx
+++ b/frontend/src/documents/DocumentSummarySection.tsx
@@ -14,11 +14,10 @@ import {
 import { describeDocumentSummary, type DocumentSummaryRow } from './documentSummary';
 
 import { useFolderManager } from '../folders/FolderManagerContext';
-
-type Identifier = string | number;
+import type { FolderId, Identifier, TagId } from '../types/identifiers';
 
 interface TagEntry {
-  id?: Identifier;
+  id?: TagId;
   label?: string;
   color?: string | null;
 }
@@ -33,7 +32,7 @@ interface DocumentLike {
   id?: Identifier;
   title?: string;
   issued_at?: string | null;
-  folder_id?: string | null;
+  folder_id?: FolderId | null;
   current_version?: { version_number?: number } | null;
   tags?: TagEntry[];
   correspondents?: CorrespondentEntry[];
@@ -64,17 +63,17 @@ interface CorrespondentSectionProps {
 
 export interface DocumentSummarySectionProps {
   document?: DocumentLike | null;
-  tagLookupById?: Map<Identifier, TagEntry>;
+  tagLookupById?: Map<TagId, TagEntry>;
   tagOptions?: SelectionAssignmentMenuItem[];
   onTagAdd?: (doc: DocumentLike, value: string, context?: { option?: unknown }) => void;
-  onTagRemove?: (docId: Identifier | undefined, tagId: Identifier | undefined) => void;
+  onTagRemove?: (docId: Identifier | undefined, tagId: TagId | undefined) => void;
   correspondents?: CorrespondentEntry[];
   correspondentOptions?: SelectionAssignmentMenuItem[];
   onCorrespondentAdd?: (payload: { document: DocumentLike; name: string; option?: unknown }) => void;
   onCorrespondentRemove?: (payload: { documentId: Identifier | undefined; correspondentId: Identifier | undefined }) => void;
   onUpdateTitle?: (docId: Identifier | undefined, title: string) => Promise<boolean> | boolean;
   onUpdateIssued?: (docId: Identifier | undefined, timestamp: number | null) => Promise<boolean> | boolean;
-  onFolderNavigate?: (folderId: string | null) => void;
+  onFolderNavigate?: (folderId: FolderId | null) => void;
   layout?: 'default' | 'compact';
 }
 
diff --git a/frontend/src/documents/DocumentThumbnailImage.tsx b/frontend/src/documents/DocumentThumbnailImage.tsx
index 70548c9..8b9a1ae 100644
--- a/frontend/src/documents/DocumentThumbnailImage.tsx
+++ b/frontend/src/documents/DocumentThumbnailImage.tsx
@@ -17,7 +17,7 @@ const DEFAULT_THUMBNAIL_SIZE = 48;
 // Detect when an element becomes visible within a scroll container so we can delay loading.
 const useLazyVisibility = (
   rootRef: MutableRefObject<Element | null> | null,
-  resetKey?: string | number | null,
+  resetKey?: string | null,
 ) => {
   const targetRef = useRef<HTMLDivElement | null>(null);
   const [isVisible, setIsVisible] = useState(false);
diff --git a/frontend/src/documents/DocumentsGrid.tsx b/frontend/src/documents/DocumentsGrid.tsx
index f9f0c99..c942d91 100644
--- a/frontend/src/documents/DocumentsGrid.tsx
+++ b/frontend/src/documents/DocumentsGrid.tsx
@@ -8,8 +8,7 @@ import { resolveCorrespondents } from './correspondents';
 import { writeTagTransferData } from './tagTransfer';
 import useInlineRename from './useInlineRename';
 import { useWorkspaceSelectionContext } from '../app/WorkspaceSelectionContext';
-
-export type Identifier = string | number;
+import type { Identifier } from '../types/identifiers';
 
 export interface FolderLike {
   id?: Identifier | 'root';
@@ -153,347 +152,347 @@ const DocumentsGrid: React.FC<DocumentsGridProps> = ({
   const totalSelectionCount = documentSelectionCount + folderSelectionCount;
 
   return (
-  <div
-    className="documents-grid"
-    role="list"
-    style={{ '--documents-grid-icon-size': `${gridIconSize}px` }}
-    onClick={(event) => {
-      if (event.target === event.currentTarget) {
+    <div
+      className="documents-grid"
+      role="list"
+      style={{ '--documents-grid-icon-size': `${gridIconSize}px` }}
+      onClick={(event) => {
+        if (event.target === event.currentTarget) {
           clearSelection();
-      }
-    }}
-  >
-    {entries.map((entry) => {
-      if (entry.type === 'folder') {
-        const folder = entry.folder;
-        if (!folder) {
-          return null;
         }
-        const canDragFolder = folder.id !== 'root';
-        const isDraggingFolder = draggedFolderId === folder.id;
-        const isSelectedFolder = selectedFolderIdsSet?.has(folder.id);
-        const classes = ['document-card', 'folder-card'];
-        if (isDraggingFolder) classes.push('is-dragging');
-        if (isSelectedFolder) classes.push('selected');
-        const canRenameFolder = Boolean(onFolderRename) && folder.id !== 'root';
-        const isFolderEditing = editingFolderId === folder.id;
-        const folderDraftValue = isFolderEditing ? folderDraft : folder.name;
-        const trimmedFolderDraft = isFolderEditing ? folderDraft.trim() : '';
-        const isFolderSaving = savingFolderId === folder.id;
-        const canSubmitFolder =
-          isFolderEditing && trimmedFolderDraft.length > 0 && trimmedFolderDraft !== folder.name;
-        const allowInlineFolderEdit = canRenameFolder && isSelectedFolder && totalSelectionCount === 1;
+      }}
+    >
+      {entries.map((entry) => {
+        if (entry.type === 'folder') {
+          const folder = entry.folder;
+          if (!folder) {
+            return null;
+          }
+          const canDragFolder = folder.id !== 'root';
+          const isDraggingFolder = draggedFolderId === folder.id;
+          const isSelectedFolder = selectedFolderIdsSet?.has(folder.id);
+          const classes = ['document-card', 'folder-card'];
+          if (isDraggingFolder) classes.push('is-dragging');
+          if (isSelectedFolder) classes.push('selected');
+          const canRenameFolder = Boolean(onFolderRename) && folder.id !== 'root';
+          const isFolderEditing = editingFolderId === folder.id;
+          const folderDraftValue = isFolderEditing ? folderDraft : folder.name;
+          const trimmedFolderDraft = isFolderEditing ? folderDraft.trim() : '';
+          const isFolderSaving = savingFolderId === folder.id;
+          const canSubmitFolder =
+            isFolderEditing && trimmedFolderDraft.length > 0 && trimmedFolderDraft !== folder.name;
+          const allowInlineFolderEdit = canRenameFolder && isSelectedFolder && totalSelectionCount === 1;
 
-        return (
-          <div
-            key={entry.key}
-            className={classes.join(' ')}
-            role="listitem"
-            id={`folder-card-${folder.id}`}
-            draggable={canDragFolder}
-            onClick={(event) => onFolderClick?.(folder, event)}
-            onDoubleClick={(event) => {
-              event.preventDefault();
-              onFolderSelect?.(folder.id);
-            }}
-            onDragOver={(event) => onFolderDragOver?.(event, folder.id)}
-            onDragLeave={onFolderDragLeave}
-            onDrop={(event) => onFolderDrop?.(event, folder.id)}
-            onDragStart={(event) => {
-              if (canDragFolder) {
-                onFolderDragStart?.(event, folder.id);
-              }
-            }}
-            onDragEnd={(event) => {
-              if (canDragFolder) {
-                onFolderDragEnd?.(event);
-              }
-            }}
-          >
-            <div className="folder-card__icon">
-              <FolderIcon className="folder-card__icon-svg" size={gridIconSize} />
-            </div>
-            <div className="folder-card__meta">
-              {isFolderEditing ? (
-                <div className="folder-card__edit doc-title-edit">
-                  <input
-                    type="text"
-                    ref={attachFolderInputRef}
-                    value={folderDraftValue}
-                    onChange={(event) => setFolderDraft(event.target.value)}
-                    onClick={(event) => event.stopPropagation()}
-                    onKeyDown={(event) => {
-                      if (event.key === 'Enter') {
-                        event.preventDefault();
+          return (
+            <div
+              key={entry.key}
+              className={classes.join(' ')}
+              role="listitem"
+              id={`folder-card-${folder.id}`}
+              draggable={canDragFolder}
+              onClick={(event) => onFolderClick?.(folder, event)}
+              onDoubleClick={(event) => {
+                event.preventDefault();
+                onFolderSelect?.(folder.id);
+              }}
+              onDragOver={(event) => onFolderDragOver?.(event, folder.id)}
+              onDragLeave={onFolderDragLeave}
+              onDrop={(event) => onFolderDrop?.(event, folder.id)}
+              onDragStart={(event) => {
+                if (canDragFolder) {
+                  onFolderDragStart?.(event, folder.id);
+                }
+              }}
+              onDragEnd={(event) => {
+                if (canDragFolder) {
+                  onFolderDragEnd?.(event);
+                }
+              }}
+            >
+              <div className="folder-card__icon">
+                <FolderIcon className="folder-card__icon-svg" size={gridIconSize} />
+              </div>
+              <div className="folder-card__meta">
+                {isFolderEditing ? (
+                  <div className="folder-card__edit doc-title-edit">
+                    <input
+                      type="text"
+                      ref={attachFolderInputRef}
+                      value={folderDraftValue}
+                      onChange={(event) => setFolderDraft(event.target.value)}
+                      onClick={(event) => event.stopPropagation()}
+                      onKeyDown={(event) => {
+                        if (event.key === 'Enter') {
+                          event.preventDefault();
+                          submitFolderEditing(folder);
+                        } else if (event.key === 'Escape') {
+                          event.preventDefault();
+                          cancelFolderEditing(event);
+                        }
+                      }}
+                      onBlur={(event) => {
+                        const nextFocus = event.relatedTarget;
+                        if (!nextFocus || !event.currentTarget.parentElement?.contains(nextFocus)) {
+                          cancelFolderEditing();
+                        }
+                      }}
+                    />
+                    <button
+                      type="button"
+                      className="icon-button"
+                      aria-label="Save name"
+                      title="Save name"
+                      disabled={!canSubmitFolder || isFolderSaving}
+                      onClick={(event) => {
+                        event.stopPropagation();
                         submitFolderEditing(folder);
-                      } else if (event.key === 'Escape') {
-                        event.preventDefault();
-                        cancelFolderEditing(event);
-                      }
-                    }}
-                    onBlur={(event) => {
-                      const nextFocus = event.relatedTarget;
-                      if (!nextFocus || !event.currentTarget.parentElement?.contains(nextFocus)) {
-                        cancelFolderEditing();
-                      }
-                    }}
-                  />
-                  <button
-                    type="button"
-                    className="icon-button"
-                    aria-label="Save name"
-                    title="Save name"
-                    disabled={!canSubmitFolder || isFolderSaving}
-                    onClick={(event) => {
-                      event.stopPropagation();
-                      submitFolderEditing(folder);
-                    }}
-                  >
-                    <CheckIcon />
-                  </button>
-                  <button
-                    type="button"
-                    className="icon-button"
-                    aria-label="Cancel"
-                    title="Cancel"
-                    onClick={(event) => cancelFolderEditing(event)}
-                  >
-                    <CloseIcon />
-                  </button>
-                </div>
-              ) : (
-                <div className="folder-card__label-row">
-                  <span
-                    className="folder-card__name"
-                    title={folder.name}
-                    role={allowInlineFolderEdit ? 'button' : undefined}
-                    tabIndex={allowInlineFolderEdit ? 0 : undefined}
-                    onClick={(event) => {
-                      if (!allowInlineFolderEdit) {
-                        return;
-                      }
-                      event.preventDefault();
-                      event.stopPropagation();
-                      beginFolderEditing(folder);
-                    }}
-                    onKeyDown={(event) => {
-                      if (!allowInlineFolderEdit) {
-                        return;
-                      }
-                      if (event.key === 'Enter') {
+                      }}
+                    >
+                      <CheckIcon />
+                    </button>
+                    <button
+                      type="button"
+                      className="icon-button"
+                      aria-label="Cancel"
+                      title="Cancel"
+                      onClick={(event) => cancelFolderEditing(event)}
+                    >
+                      <CloseIcon />
+                    </button>
+                  </div>
+                ) : (
+                  <div className="folder-card__label-row">
+                    <span
+                      className="folder-card__name"
+                      title={folder.name}
+                      role={allowInlineFolderEdit ? 'button' : undefined}
+                      tabIndex={allowInlineFolderEdit ? 0 : undefined}
+                      onClick={(event) => {
+                        if (!allowInlineFolderEdit) {
+                          return;
+                        }
                         event.preventDefault();
                         event.stopPropagation();
                         beginFolderEditing(folder);
-                      }
-                    }}
-                  >
-                    {folder.name}
-                  </span>
-                </div>
-              )}
+                      }}
+                      onKeyDown={(event) => {
+                        if (!allowInlineFolderEdit) {
+                          return;
+                        }
+                        if (event.key === 'Enter') {
+                          event.preventDefault();
+                          event.stopPropagation();
+                          beginFolderEditing(folder);
+                        }
+                      }}
+                    >
+                      {folder.name}
+                    </span>
+                  </div>
+                )}
+              </div>
             </div>
-          </div>
-        );
-      }
+          );
+        }
 
-      const doc = entry.document;
-      if (!doc) {
-        return null;
-      }
+        const doc = entry.document;
+        if (!doc) {
+          return null;
+        }
 
-      const isSelected = selectedDocumentIdsSet?.has(doc.id);
-      const isDraggingDoc = draggingDocumentIdsSet?.has(doc.id);
-      const tagList = Array.isArray(doc.tags) ? doc.tags : [];
-      const visibleTags = tagList.slice(0, 3);
-      const remainingTagCount = tagList.length > 3 ? tagList.length - 3 : 0;
-      const correspondents = resolveCorrespondents(doc);
-      const cardClasses = ['document-card', 'document'];
-      if (isSelected) cardClasses.push('selected');
-      if (isDraggingDoc) cardClasses.push('is-dragging');
-      const isEditingDoc = editingDocumentId === doc.id;
-      const documentDraftValue = isEditingDoc ? documentDraft : doc.title;
-      const trimmedDocumentDraft = isEditingDoc ? documentDraft.trim() : '';
-      const isDocumentSaving = savingDocumentId === doc.id;
-      const canSubmitDocument =
-        isEditingDoc && trimmedDocumentDraft.length > 0 && trimmedDocumentDraft !== doc.title;
-      const allowInlineDocumentEdit = onDocumentRename && isSelected && totalSelectionCount === 1;
-      return (
-        <div
-          key={entry.key}
-          className={cardClasses.join(' ')}
-          role="listitem"
-          id={`document-card-${doc.id}`}
-          data-doc-id={doc.id}
-          onClick={(event) => onDocumentClick?.(doc, event)}
-          onDoubleClick={(event) => onDocumentActivate?.(doc, event)}
-          draggable
-          onDragStart={(event) => onDocumentDragStart?.(event, doc)}
-          onDragEnd={(event) => onDocumentDragEnd?.(event)}
-          onDragOver={(event) => onDocumentTagDragOver?.(event)}
-          onDragOverCapture={(event) => onDocumentTagDragOver?.(event)}
-          onDragLeave={onDocumentTagDragLeave}
-          onDragLeaveCapture={onDocumentTagDragLeave}
-          onDrop={(event) => onDocumentTagDrop?.(event, doc.id)}
-          onDropCapture={(event) => onDocumentTagDrop?.(event, doc.id)}
-        >
-          <DocumentThumbnailImage
-            document={doc}
-            ensureAssetUrl={ensureAssetUrl}
-            getDocumentAsset={getDocumentAsset}
-            alt={`Thumbnail for ${doc.title}`}
-            maxSize={gridIconSize}
-            scrollRootRef={scrollRef}
-          />
-          <div className="document-card__meta">
-            <div className="document-card__title" title={doc.title}>
-              {correspondents.length > 0 ? (
-                <span className="doc-correspondents">
-                  <CorrespondentLinks
-                    correspondents={correspondents}
-                    activeCorrespondentIdSet={activeCorrespondentIdSet}
-                    onCorrespondentClick={onCorrespondentClick}
-                  />
-                </span>
-              ) : null}
-              {isEditingDoc ? (
-                <div className="document-card__title-edit doc-title-edit">
-                  <input
-                    type="text"
-                    ref={attachDocumentInputRef}
-                    value={documentDraftValue}
-                    onChange={(event) => setDocumentDraft(event.target.value)}
-                    onClick={(event) => event.stopPropagation()}
-                    onKeyDown={(event) => {
-                      if (event.key === 'Enter') {
-                        event.preventDefault();
+        const isSelected = selectedDocumentIdsSet?.has(doc.id);
+        const isDraggingDoc = draggingDocumentIdsSet?.has(doc.id);
+        const tagList = Array.isArray(doc.tags) ? doc.tags : [];
+        const visibleTags = tagList.slice(0, 3);
+        const remainingTagCount = tagList.length > 3 ? tagList.length - 3 : 0;
+        const correspondents = resolveCorrespondents(doc);
+        const cardClasses = ['document-card', 'document'];
+        if (isSelected) cardClasses.push('selected');
+        if (isDraggingDoc) cardClasses.push('is-dragging');
+        const isEditingDoc = editingDocumentId === doc.id;
+        const documentDraftValue = isEditingDoc ? documentDraft : doc.title;
+        const trimmedDocumentDraft = isEditingDoc ? documentDraft.trim() : '';
+        const isDocumentSaving = savingDocumentId === doc.id;
+        const canSubmitDocument =
+          isEditingDoc && trimmedDocumentDraft.length > 0 && trimmedDocumentDraft !== doc.title;
+        const allowInlineDocumentEdit = onDocumentRename && isSelected && totalSelectionCount === 1;
+        return (
+          <div
+            key={entry.key}
+            className={cardClasses.join(' ')}
+            role="listitem"
+            id={`document-card-${doc.id}`}
+            data-doc-id={doc.id}
+            onClick={(event) => onDocumentClick?.(doc, event)}
+            onDoubleClick={(event) => onDocumentActivate?.(doc, event)}
+            draggable
+            onDragStart={(event) => onDocumentDragStart?.(event, doc)}
+            onDragEnd={(event) => onDocumentDragEnd?.(event)}
+            onDragOver={(event) => onDocumentTagDragOver?.(event)}
+            onDragOverCapture={(event) => onDocumentTagDragOver?.(event)}
+            onDragLeave={onDocumentTagDragLeave}
+            onDragLeaveCapture={onDocumentTagDragLeave}
+            onDrop={(event) => onDocumentTagDrop?.(event, doc.id)}
+            onDropCapture={(event) => onDocumentTagDrop?.(event, doc.id)}
+          >
+            <DocumentThumbnailImage
+              document={doc}
+              ensureAssetUrl={ensureAssetUrl}
+              getDocumentAsset={getDocumentAsset}
+              alt={`Thumbnail for ${doc.title}`}
+              maxSize={gridIconSize}
+              scrollRootRef={scrollRef}
+            />
+            <div className="document-card__meta">
+              <div className="document-card__title" title={doc.title}>
+                {correspondents.length > 0 ? (
+                  <span className="doc-correspondents">
+                    <CorrespondentLinks
+                      correspondents={correspondents}
+                      activeCorrespondentIdSet={activeCorrespondentIdSet}
+                      onCorrespondentClick={onCorrespondentClick}
+                    />
+                  </span>
+                ) : null}
+                {isEditingDoc ? (
+                  <div className="document-card__title-edit doc-title-edit">
+                    <input
+                      type="text"
+                      ref={attachDocumentInputRef}
+                      value={documentDraftValue}
+                      onChange={(event) => setDocumentDraft(event.target.value)}
+                      onClick={(event) => event.stopPropagation()}
+                      onKeyDown={(event) => {
+                        if (event.key === 'Enter') {
+                          event.preventDefault();
+                          submitDocumentEditing(doc);
+                        } else if (event.key === 'Escape') {
+                          event.preventDefault();
+                          cancelDocumentEditing(event);
+                        }
+                      }}
+                      onBlur={(event) => {
+                        const nextFocus = event.relatedTarget;
+                        if (!nextFocus || !event.currentTarget.parentElement?.contains(nextFocus)) {
+                          cancelDocumentEditing();
+                        }
+                      }}
+                    />
+                    <button
+                      type="button"
+                      className="icon-button"
+                      aria-label="Save title"
+                      title="Save title"
+                      disabled={!canSubmitDocument || isDocumentSaving}
+                      onClick={(event) => {
+                        event.stopPropagation();
                         submitDocumentEditing(doc);
-                      } else if (event.key === 'Escape') {
-                        event.preventDefault();
-                        cancelDocumentEditing(event);
-                      }
-                    }}
-                    onBlur={(event) => {
-                      const nextFocus = event.relatedTarget;
-                      if (!nextFocus || !event.currentTarget.parentElement?.contains(nextFocus)) {
-                        cancelDocumentEditing();
-                      }
-                    }}
-                  />
-                  <button
-                    type="button"
-                    className="icon-button"
-                    aria-label="Save title"
-                    title="Save title"
-                    disabled={!canSubmitDocument || isDocumentSaving}
-                    onClick={(event) => {
-                      event.stopPropagation();
-                      submitDocumentEditing(doc);
-                    }}
-                  >
-                    <CheckIcon />
-                  </button>
-                  <button
-                    type="button"
-                    className="icon-button"
-                    aria-label="Cancel"
-                    title="Cancel"
-                    onClick={(event) => cancelDocumentEditing(event)}
-                  >
-                    <CloseIcon />
-                  </button>
-                </div>
-              ) : (
-                <div className="document-card__title-row">
-                  <span
-                    className="document-card__title-badge"
-                    role={allowInlineDocumentEdit ? 'button' : undefined}
-                    tabIndex={allowInlineDocumentEdit ? 0 : undefined}
-                    onClick={(event) => {
-                      if (!allowInlineDocumentEdit) {
-                        return;
-                      }
-                      event.preventDefault();
-                      event.stopPropagation();
-                      beginDocumentEditing(doc);
-                    }}
-                    onKeyDown={(event) => {
-                      if (!allowInlineDocumentEdit) {
-                        return;
-                      }
-                      if (event.key === 'Enter') {
+                      }}
+                    >
+                      <CheckIcon />
+                    </button>
+                    <button
+                      type="button"
+                      className="icon-button"
+                      aria-label="Cancel"
+                      title="Cancel"
+                      onClick={(event) => cancelDocumentEditing(event)}
+                    >
+                      <CloseIcon />
+                    </button>
+                  </div>
+                ) : (
+                  <div className="document-card__title-row">
+                    <span
+                      className="document-card__title-badge"
+                      role={allowInlineDocumentEdit ? 'button' : undefined}
+                      tabIndex={allowInlineDocumentEdit ? 0 : undefined}
+                      onClick={(event) => {
+                        if (!allowInlineDocumentEdit) {
+                          return;
+                        }
                         event.preventDefault();
                         event.stopPropagation();
                         beginDocumentEditing(doc);
-                      }
-                    }}
-                  >
-                    {doc.title}
-                  </span>
-                </div>
-              )}
-            </div>
-            {visibleTags.length > 0 && (
-              <div className="document-card__tags">
-                {visibleTags.map((tag, index) => {
-                  const colorSource = tag?.color || tagLookupById?.get(tag.id)?.color;
-                  const style = getTagColorStyle(colorSource);
-                  const tagId = tag?.id ?? null;
-                  const clickable = tagId != null && typeof onTagClick === 'function';
-                  const key = tagId ?? `${doc.id}-tag-${index}`;
-                  return (
-                    <span
-                      key={key}
-                      className="badge tag-chip"
-                      style={style || undefined}
-                      title={tag.label}
-                      role={clickable ? 'button' : undefined}
-                      onClick={clickable ? (event) => {
-                        event.stopPropagation();
-                        if (tagId == null) {
+                      }}
+                      onKeyDown={(event) => {
+                        if (!allowInlineDocumentEdit) {
                           return;
                         }
-                        onTagClick?.(tagId);
-                      } : undefined}
-                      draggable
-                      onDragStart={(event) => {
-                        event.stopPropagation();
-                        try {
-                          if (event.dataTransfer) {
-                            event.dataTransfer.effectAllowed = 'copyMove';
-                          }
-                        } catch (error) {
-                          console.warn('[documents] Failed to configure drag effect', error);
-                        }
-                        writeTagTransferData(event.dataTransfer, tag, doc.id);
-                      }}
-                      onDragEnd={(event) => {
-                        event.stopPropagation();
-                      }}
-                      onKeyDown={clickable ? (event) => {
-                        if (event.key === 'Enter' || event.key === ' ') {
+                        if (event.key === 'Enter') {
                           event.preventDefault();
+                          event.stopPropagation();
+                          beginDocumentEditing(doc);
+                        }
+                      }}
+                    >
+                      {doc.title}
+                    </span>
+                  </div>
+                )}
+              </div>
+              {visibleTags.length > 0 && (
+                <div className="document-card__tags">
+                  {visibleTags.map((tag, index) => {
+                    const colorSource = tag?.color || tagLookupById?.get(tag.id)?.color;
+                    const style = getTagColorStyle(colorSource);
+                    const tagId = tag?.id ?? null;
+                    const clickable = tagId != null && typeof onTagClick === 'function';
+                    const key = tagId ?? `${doc.id}-tag-${index}`;
+                    return (
+                      <span
+                        key={key}
+                        className="badge tag-chip"
+                        style={style || undefined}
+                        title={tag.label}
+                        role={clickable ? 'button' : undefined}
+                        onClick={clickable ? (event) => {
                           event.stopPropagation();
                           if (tagId == null) {
                             return;
                           }
                           onTagClick?.(tagId);
-                        }
-                      } : undefined}
-                    >
-                      {tag.label}
-                    </span>
-                  );
-                })}
-                {remainingTagCount > 0 && (
-                  <span className="badge tag-chip tag-chip--more">+{remainingTagCount}</span>
-                )}
-              </div>
-            )}
+                        } : undefined}
+                        draggable
+                        onDragStart={(event) => {
+                          event.stopPropagation();
+                          try {
+                            if (event.dataTransfer) {
+                              event.dataTransfer.effectAllowed = 'copyMove';
+                            }
+                          } catch (error) {
+                            console.warn('[documents] Failed to configure drag effect', error);
+                          }
+                          writeTagTransferData(event.dataTransfer, tag, doc.id);
+                        }}
+                        onDragEnd={(event) => {
+                          event.stopPropagation();
+                        }}
+                        onKeyDown={clickable ? (event) => {
+                          if (event.key === 'Enter' || event.key === ' ') {
+                            event.preventDefault();
+                            event.stopPropagation();
+                            if (tagId == null) {
+                              return;
+                            }
+                            onTagClick?.(tagId);
+                          }
+                        } : undefined}
+                      >
+                        {tag.label}
+                      </span>
+                    );
+                  })}
+                  {remainingTagCount > 0 && (
+                    <span className="badge tag-chip tag-chip--more">+{remainingTagCount}</span>
+                  )}
+                </div>
+              )}
+            </div>
           </div>
-        </div>
-      );
-    })}
-  </div>
+        );
+      })}
+    </div>
   );
 };
 
diff --git a/frontend/src/documents/DocumentsList.tsx b/frontend/src/documents/DocumentsList.tsx
index 570e71d..3ea8284 100644
--- a/frontend/src/documents/DocumentsList.tsx
+++ b/frontend/src/documents/DocumentsList.tsx
@@ -9,8 +9,7 @@ import { resolveCorrespondents } from './correspondents';
 import { writeTagTransferData } from './tagTransfer';
 import useInlineRename from './useInlineRename';
 import { useWorkspaceSelectionContext } from '../app/WorkspaceSelectionContext';
-
-export type Identifier = string | number;
+import type { Identifier } from '../types/identifiers';
 
 export interface FolderLike {
   id?: Identifier | 'root';
@@ -160,356 +159,356 @@ const DocumentsList: React.FC<DocumentsListProps> = ({
   const totalSelectionCount = documentSelectionCount + folderSelectionCount;
 
   return (
-  <table aria-multiselectable="true">
-    <thead
-      onClick={() => {
-        clearSelection();
-      }}
-    >
-      <tr>
-        <th>&nbsp;</th>
-        <th>Name</th>
-        <th>Issued</th>
-        <th>Added</th>
-      </tr>
-    </thead>
-    <tbody>
-      {entries.map((entry) => {
-        if (entry.type === 'folder') {
-          const folder = entry.folder;
-          if (!folder) {
-            return null;
-          }
-          const canDragFolder = folder.id !== 'root';
-          const isDraggingFolder = draggedFolderId === folder.id;
-          const isSelectedFolder = selectedFolderIdsSet?.has(folder.id);
-          const canRenameFolder = Boolean(onFolderRename) && folder.id !== 'root';
-          const isFolderEditing = editingFolderId === folder.id;
-          const folderDraftValue = isFolderEditing ? folderDraft : folder.name;
-          const trimmedFolderDraft = isFolderEditing ? folderDraft.trim() : '';
-          const isFolderSaving = savingFolderId === folder.id;
-          const canSubmitFolder =
-            isFolderEditing && trimmedFolderDraft.length > 0 && trimmedFolderDraft !== folder.name;
-          const allowInlineFolderEdit = canRenameFolder && isSelectedFolder && totalSelectionCount === 1;
+    <table aria-multiselectable="true">
+      <thead
+        onClick={() => {
+          clearSelection();
+        }}
+      >
+        <tr>
+          <th>&nbsp;</th>
+          <th>Name</th>
+          <th>Issued</th>
+          <th>Added</th>
+        </tr>
+      </thead>
+      <tbody>
+        {entries.map((entry) => {
+          if (entry.type === 'folder') {
+            const folder = entry.folder;
+            if (!folder) {
+              return null;
+            }
+            const canDragFolder = folder.id !== 'root';
+            const isDraggingFolder = draggedFolderId === folder.id;
+            const isSelectedFolder = selectedFolderIdsSet?.has(folder.id);
+            const canRenameFolder = Boolean(onFolderRename) && folder.id !== 'root';
+            const isFolderEditing = editingFolderId === folder.id;
+            const folderDraftValue = isFolderEditing ? folderDraft : folder.name;
+            const trimmedFolderDraft = isFolderEditing ? folderDraft.trim() : '';
+            const isFolderSaving = savingFolderId === folder.id;
+            const canSubmitFolder =
+              isFolderEditing && trimmedFolderDraft.length > 0 && trimmedFolderDraft !== folder.name;
+            const allowInlineFolderEdit = canRenameFolder && isSelectedFolder && totalSelectionCount === 1;
 
-          return (
-            <tr
-              key={entry.key}
-              className={`folder${isDraggingFolder ? ' is-dragging' : ''}${isSelectedFolder ? ' selected' : ''}`}
-              id={`folder-row-${folder.id}`}
-              onClick={(event) => onFolderClick?.(folder, event)}
-              onDoubleClick={(event) => {
-                event.preventDefault();
-                onFolderSelect?.(folder.id);
-              }}
-              onDragOver={(event) => onFolderDragOver?.(event, folder.id)}
-              onDragLeave={onFolderDragLeave}
-              onDrop={(event) => onFolderDrop?.(event, folder.id)}
-              draggable={canDragFolder}
-              onDragStart={(event) => {
-                if (canDragFolder) {
-                  onFolderDragStart?.(event, folder.id);
-                }
-              }}
-              onDragEnd={(event) => {
-                if (canDragFolder) {
-                  onFolderDragEnd?.(event);
-                }
-              }}
-            >
-              <td className="thumb-cell">
-                <div className="thumb-icon">
-                  <FolderIcon className="thumb-icon__image" size={32} />
-                </div>
-              </td>
-              <td className="doc-list__name">
-                <div className="doc-list__name-content">
-                  <span className="doc-name__title">
-                    <span className="doc-name__primary">
-                      {isFolderEditing ? (
-                        <span className="doc-title-edit">
-                          <input
-                            type="text"
-                            ref={attachFolderInputRef}
-                            value={folderDraftValue}
-                            onChange={(event) => setFolderDraft(event.target.value)}
-                            onClick={(event) => event.stopPropagation()}
-                            onKeyDown={(event) => {
-                              if (event.key === 'Enter') {
-                                event.preventDefault();
+            return (
+              <tr
+                key={entry.key}
+                className={`folder${isDraggingFolder ? ' is-dragging' : ''}${isSelectedFolder ? ' selected' : ''}`}
+                id={`folder-row-${folder.id}`}
+                onClick={(event) => onFolderClick?.(folder, event)}
+                onDoubleClick={(event) => {
+                  event.preventDefault();
+                  onFolderSelect?.(folder.id);
+                }}
+                onDragOver={(event) => onFolderDragOver?.(event, folder.id)}
+                onDragLeave={onFolderDragLeave}
+                onDrop={(event) => onFolderDrop?.(event, folder.id)}
+                draggable={canDragFolder}
+                onDragStart={(event) => {
+                  if (canDragFolder) {
+                    onFolderDragStart?.(event, folder.id);
+                  }
+                }}
+                onDragEnd={(event) => {
+                  if (canDragFolder) {
+                    onFolderDragEnd?.(event);
+                  }
+                }}
+              >
+                <td className="thumb-cell">
+                  <div className="thumb-icon">
+                    <FolderIcon className="thumb-icon__image" size={32} />
+                  </div>
+                </td>
+                <td className="doc-list__name">
+                  <div className="doc-list__name-content">
+                    <span className="doc-name__title">
+                      <span className="doc-name__primary">
+                        {isFolderEditing ? (
+                          <span className="doc-title-edit">
+                            <input
+                              type="text"
+                              ref={attachFolderInputRef}
+                              value={folderDraftValue}
+                              onChange={(event) => setFolderDraft(event.target.value)}
+                              onClick={(event) => event.stopPropagation()}
+                              onKeyDown={(event) => {
+                                if (event.key === 'Enter') {
+                                  event.preventDefault();
+                                  submitFolderEditing(folder);
+                                } else if (event.key === 'Escape') {
+                                  event.preventDefault();
+                                  cancelFolderEditing(event);
+                                }
+                              }}
+                              onBlur={(event) => {
+                                const nextFocus = event.relatedTarget;
+                                if (!nextFocus || !event.currentTarget.parentElement?.contains(nextFocus)) {
+                                  cancelFolderEditing();
+                                }
+                              }}
+                            />
+                            <button
+                              type="button"
+                              className="icon-button"
+                              aria-label="Save name"
+                              title="Save name"
+                              disabled={!canSubmitFolder || isFolderSaving}
+                              onClick={(event) => {
+                                event.stopPropagation();
                                 submitFolderEditing(folder);
-                              } else if (event.key === 'Escape') {
-                                event.preventDefault();
+                              }}
+                            >
+                              <CheckIcon />
+                            </button>
+                            <button
+                              type="button"
+                              className="icon-button"
+                              aria-label="Cancel"
+                              title="Cancel"
+                              onClick={(event) => {
                                 cancelFolderEditing(event);
-                              }
-                            }}
-                            onBlur={(event) => {
-                              const nextFocus = event.relatedTarget;
-                              if (!nextFocus || !event.currentTarget.parentElement?.contains(nextFocus)) {
-                                cancelFolderEditing();
-                              }
-                            }}
-                          />
-                          <button
-                            type="button"
-                            className="icon-button"
-                            aria-label="Save name"
-                            title="Save name"
-                            disabled={!canSubmitFolder || isFolderSaving}
+                              }}
+                            >
+                              <CloseIcon />
+                            </button>
+                          </span>
+                        ) : (
+                          <span
+                            className="doc-name__primary-text"
+                            role={allowInlineFolderEdit ? 'button' : undefined}
+                            tabIndex={allowInlineFolderEdit ? 0 : undefined}
                             onClick={(event) => {
-                              event.stopPropagation();
-                              submitFolderEditing(folder);
-                            }}
-                          >
-                            <CheckIcon />
-                          </button>
-                          <button
-                            type="button"
-                            className="icon-button"
-                            aria-label="Cancel"
-                            title="Cancel"
-                            onClick={(event) => {
-                              cancelFolderEditing(event);
-                            }}
-                          >
-                            <CloseIcon />
-                          </button>
-                        </span>
-                      ) : (
-                        <span
-                          className="doc-name__primary-text"
-                          role={allowInlineFolderEdit ? 'button' : undefined}
-                          tabIndex={allowInlineFolderEdit ? 0 : undefined}
-                          onClick={(event) => {
-                            if (!allowInlineFolderEdit) {
-                              return;
-                            }
-                            event.preventDefault();
-                            event.stopPropagation();
-                            beginFolderEditing(folder);
-                          }}
-                          onKeyDown={(event) => {
-                            if (!allowInlineFolderEdit) {
-                              return;
-                            }
-                            if (event.key === 'Enter') {
+                              if (!allowInlineFolderEdit) {
+                                return;
+                              }
                               event.preventDefault();
                               event.stopPropagation();
                               beginFolderEditing(folder);
-                            }
-                          }}
-                        >
-                          {folder.name}
-                        </span>
-                      )}
-                    </span>
-                  </span>
-                </div>
-              </td>
-              <td>—</td>
-              <td>—</td>
-            </tr>
-          );
-        }
-
-        const doc = entry.document;
-        if (!doc) {
-          return null;
-        }
-        const isSelected = selectedDocumentIdsSet?.has(doc.id);
-        const isDraggingDoc = draggingDocumentIdsSet?.has(doc.id);
-        const rowClasses = ['document'];
-        if (isSelected) rowClasses.push('selected');
-        if (isDraggingDoc) rowClasses.push('is-dragging');
-        const correspondents = resolveCorrespondents(doc);
-        const isEditingDoc = editingDocumentId === doc.id;
-        const documentDraftValue = isEditingDoc ? documentDraft : doc.title;
-        const trimmedDocumentDraft = isEditingDoc ? documentDraft.trim() : '';
-        const isDocumentSaving = savingDocumentId === doc.id;
-        const canSubmitDocument =
-          isEditingDoc && trimmedDocumentDraft.length > 0 && trimmedDocumentDraft !== doc.title;
-        const allowInlineDocumentEdit =
-          onDocumentRename && isSelected && totalSelectionCount === 1;
-        const issuedLabel = formatDate(doc.issued_at);
-        const addedLabel = formatDate(doc.created_at || doc.uploaded_at);
-        return (
-          <tr
-            key={entry.key}
-            className={rowClasses.join(' ')}
-            id={`document-row-${doc.id}`}
-            data-doc-id={doc.id}
-            onClick={(event) => onDocumentClick?.(doc, event)}
-            onDoubleClick={(event) => onDocumentActivate?.(doc, event)}
-            draggable
-            onDragStart={(event) => onDocumentDragStart?.(event, doc)}
-            onDragEnd={(event) => onDocumentDragEnd?.(event)}
-            onDragOver={onDocumentTagDragOver}
-            onDragLeave={onDocumentTagDragLeave}
-            onDrop={(event) => onDocumentTagDrop?.(event, doc.id)}
-          >
-            <td className="thumb-cell">
-              <DocumentThumbnailImage
-                document={doc}
-                ensureAssetUrl={ensureAssetUrl}
-                getDocumentAsset={getDocumentAsset}
-                alt={`Thumbnail for ${doc.title}`}
-                scrollRootRef={scrollRef}
-              />
-            </td>
-            <td className="doc-list__name">
-              <div className="doc-name">
-                <div className="doc-list__name-content">
-                  <span className="doc-name__title">
-                    {correspondents.length > 0 ? (
-                      <span className="doc-correspondents">
-                        <CorrespondentLinks
-                          correspondents={correspondents}
-                          activeCorrespondentIdSet={activeCorrespondentIdSet}
-                          onCorrespondentClick={onCorrespondentClick}
-                        />
+                            }}
+                            onKeyDown={(event) => {
+                              if (!allowInlineFolderEdit) {
+                                return;
+                              }
+                              if (event.key === 'Enter') {
+                                event.preventDefault();
+                                event.stopPropagation();
+                                beginFolderEditing(folder);
+                              }
+                            }}
+                          >
+                            {folder.name}
+                          </span>
+                        )}
                       </span>
-                    ) : null}
-                    <span className="doc-name__primary">
-                      {isEditingDoc ? (
-                        <span className="doc-title-edit">
-                          <input
-                            type="text"
-                            ref={attachDocumentInputRef}
-                            value={documentDraftValue}
-                            onChange={(event) => setDocumentDraft(event.target.value)}
-                            onClick={(event) => event.stopPropagation()}
-                          onKeyDown={(event) => {
-                            if (event.key === 'Enter') {
-                              event.preventDefault();
-                              submitDocumentEditing(doc);
-                            } else if (event.key === 'Escape') {
-                              event.preventDefault();
-                              cancelDocumentEditing(event);
-                            }
-                          }}
-                          onBlur={(event) => {
-                            const nextFocus = event.relatedTarget;
-                            if (!nextFocus || !event.currentTarget.parentElement?.contains(nextFocus)) {
-                              cancelDocumentEditing();
-                            }
-                          }}
-                        />
-                          <button
-                            type="button"
-                            className="icon-button"
-                            aria-label="Save title"
-                            title="Save title"
-                            disabled={!canSubmitDocument || isDocumentSaving}
-                            onClick={(event) => {
-                              event.stopPropagation();
-                              submitDocumentEditing(doc);
-                            }}
-                          >
-                            <CheckIcon />
-                          </button>
-                          <button
-                            type="button"
-                            className="icon-button"
-                            aria-label="Cancel"
-                            title="Cancel"
-                            onClick={(event) => {
-                              cancelDocumentEditing(event);
-                            }}
-                          >
-                            <CloseIcon />
-                          </button>
+                    </span>
+                  </div>
+                </td>
+                <td>—</td>
+                <td>—</td>
+              </tr>
+            );
+          }
+
+          const doc = entry.document;
+          if (!doc) {
+            return null;
+          }
+          const isSelected = selectedDocumentIdsSet?.has(doc.id);
+          const isDraggingDoc = draggingDocumentIdsSet?.has(doc.id);
+          const rowClasses = ['document'];
+          if (isSelected) rowClasses.push('selected');
+          if (isDraggingDoc) rowClasses.push('is-dragging');
+          const correspondents = resolveCorrespondents(doc);
+          const isEditingDoc = editingDocumentId === doc.id;
+          const documentDraftValue = isEditingDoc ? documentDraft : doc.title;
+          const trimmedDocumentDraft = isEditingDoc ? documentDraft.trim() : '';
+          const isDocumentSaving = savingDocumentId === doc.id;
+          const canSubmitDocument =
+            isEditingDoc && trimmedDocumentDraft.length > 0 && trimmedDocumentDraft !== doc.title;
+          const allowInlineDocumentEdit =
+            onDocumentRename && isSelected && totalSelectionCount === 1;
+          const issuedLabel = formatDate(doc.issued_at);
+          const addedLabel = formatDate(doc.created_at || doc.uploaded_at);
+          return (
+            <tr
+              key={entry.key}
+              className={rowClasses.join(' ')}
+              id={`document-row-${doc.id}`}
+              data-doc-id={doc.id}
+              onClick={(event) => onDocumentClick?.(doc, event)}
+              onDoubleClick={(event) => onDocumentActivate?.(doc, event)}
+              draggable
+              onDragStart={(event) => onDocumentDragStart?.(event, doc)}
+              onDragEnd={(event) => onDocumentDragEnd?.(event)}
+              onDragOver={onDocumentTagDragOver}
+              onDragLeave={onDocumentTagDragLeave}
+              onDrop={(event) => onDocumentTagDrop?.(event, doc.id)}
+            >
+              <td className="thumb-cell">
+                <DocumentThumbnailImage
+                  document={doc}
+                  ensureAssetUrl={ensureAssetUrl}
+                  getDocumentAsset={getDocumentAsset}
+                  alt={`Thumbnail for ${doc.title}`}
+                  scrollRootRef={scrollRef}
+                />
+              </td>
+              <td className="doc-list__name">
+                <div className="doc-name">
+                  <div className="doc-list__name-content">
+                    <span className="doc-name__title">
+                      {correspondents.length > 0 ? (
+                        <span className="doc-correspondents">
+                          <CorrespondentLinks
+                            correspondents={correspondents}
+                            activeCorrespondentIdSet={activeCorrespondentIdSet}
+                            onCorrespondentClick={onCorrespondentClick}
+                          />
                         </span>
-                      ) : (
-                        <span
-                          className="doc-name__primary-text"
-                          role={allowInlineDocumentEdit ? 'button' : undefined}
-                          tabIndex={allowInlineDocumentEdit ? 0 : undefined}
-                          onClick={(event) => {
-                            if (!allowInlineDocumentEdit) {
-                              return;
-                            }
-                            event.preventDefault();
-                            event.stopPropagation();
-                            beginDocumentEditing(doc);
-                          }}
-                          onKeyDown={(event) => {
-                            if (!allowInlineDocumentEdit) {
-                              return;
-                            }
-                            if (event.key === 'Enter') {
+                      ) : null}
+                      <span className="doc-name__primary">
+                        {isEditingDoc ? (
+                          <span className="doc-title-edit">
+                            <input
+                              type="text"
+                              ref={attachDocumentInputRef}
+                              value={documentDraftValue}
+                              onChange={(event) => setDocumentDraft(event.target.value)}
+                              onClick={(event) => event.stopPropagation()}
+                              onKeyDown={(event) => {
+                                if (event.key === 'Enter') {
+                                  event.preventDefault();
+                                  submitDocumentEditing(doc);
+                                } else if (event.key === 'Escape') {
+                                  event.preventDefault();
+                                  cancelDocumentEditing(event);
+                                }
+                              }}
+                              onBlur={(event) => {
+                                const nextFocus = event.relatedTarget;
+                                if (!nextFocus || !event.currentTarget.parentElement?.contains(nextFocus)) {
+                                  cancelDocumentEditing();
+                                }
+                              }}
+                            />
+                            <button
+                              type="button"
+                              className="icon-button"
+                              aria-label="Save title"
+                              title="Save title"
+                              disabled={!canSubmitDocument || isDocumentSaving}
+                              onClick={(event) => {
+                                event.stopPropagation();
+                                submitDocumentEditing(doc);
+                              }}
+                            >
+                              <CheckIcon />
+                            </button>
+                            <button
+                              type="button"
+                              className="icon-button"
+                              aria-label="Cancel"
+                              title="Cancel"
+                              onClick={(event) => {
+                                cancelDocumentEditing(event);
+                              }}
+                            >
+                              <CloseIcon />
+                            </button>
+                          </span>
+                        ) : (
+                          <span
+                            className="doc-name__primary-text"
+                            role={allowInlineDocumentEdit ? 'button' : undefined}
+                            tabIndex={allowInlineDocumentEdit ? 0 : undefined}
+                            onClick={(event) => {
+                              if (!allowInlineDocumentEdit) {
+                                return;
+                              }
                               event.preventDefault();
                               event.stopPropagation();
                               beginDocumentEditing(doc);
-                            }
-                          }}
-                        >
-                          {doc.title}
-                        </span>
-                      )}
-                    </span>
-                  </span>
-                </div>
-                {(doc.tags || []).length > 0 && (
-                  <div className="doc-name__tags">
-                    {(doc.tags || []).map((tag, index) => {
-                      const colorSource = tag?.color || tagLookupById?.get(tag.id)?.color;
-                      const style = getTagColorStyle(colorSource);
-                      const tagId = tag?.id ?? null;
-                      const clickable = tagId != null && typeof onTagClick === 'function';
-                      const key = tagId ?? `${doc.id}-tag-${index}`;
-                      return (
-                        <span
-                          key={key}
-                          className="badge tag-chip"
-                          style={style || undefined}
-                          title={tag.label}
-                          role={clickable ? 'button' : undefined}
-                          onClick={clickable ? (event) => {
-                            event.stopPropagation();
-                            if (tagId == null) return;
-                            onTagClick?.(tagId);
-                          } : undefined}
-                          draggable
-                          onDragStart={(event) => {
-                            event.stopPropagation();
-                            try {
-                              if (event.dataTransfer) {
-                                event.dataTransfer.effectAllowed = 'copyMove';
-                              }
-                            } catch (error) {
-                              console.warn('[documents] Failed to configure drag effect', error);
-                            }
-                            writeTagTransferData(event.dataTransfer, tag, doc.id);
-                          }}
-                          onDragEnd={(event) => {
-                            event.stopPropagation();
-                          }}
-                          onKeyDown={clickable ? (event) => {
-                            if (event.key === 'Enter' || event.key === ' ') {
-                              event.preventDefault();
-                              event.stopPropagation();
-                              if (tagId == null) {
+                            }}
+                            onKeyDown={(event) => {
+                              if (!allowInlineDocumentEdit) {
                                 return;
                               }
-                              onTagClick?.(tagId);
-                            }
-                          } : undefined}
-                        >
-                          {tag.label}
-                        </span>
-                      );
-                    })}
+                              if (event.key === 'Enter') {
+                                event.preventDefault();
+                                event.stopPropagation();
+                                beginDocumentEditing(doc);
+                              }
+                            }}
+                          >
+                            {doc.title}
+                          </span>
+                        )}
+                      </span>
+                    </span>
                   </div>
-                )}
-              </div>
-            </td>
-            <td>{issuedLabel}</td>
-            <td>{addedLabel}</td>
-          </tr>
-        );
-      })}
-    </tbody>
-  </table>
+                  {(doc.tags || []).length > 0 && (
+                    <div className="doc-name__tags">
+                      {(doc.tags || []).map((tag, index) => {
+                        const colorSource = tag?.color || tagLookupById?.get(tag.id)?.color;
+                        const style = getTagColorStyle(colorSource);
+                        const tagId = tag?.id ?? null;
+                        const clickable = tagId != null && typeof onTagClick === 'function';
+                        const key = tagId ?? `${doc.id}-tag-${index}`;
+                        return (
+                          <span
+                            key={key}
+                            className="badge tag-chip"
+                            style={style || undefined}
+                            title={tag.label}
+                            role={clickable ? 'button' : undefined}
+                            onClick={clickable ? (event) => {
+                              event.stopPropagation();
+                              if (tagId == null) return;
+                              onTagClick?.(tagId);
+                            } : undefined}
+                            draggable
+                            onDragStart={(event) => {
+                              event.stopPropagation();
+                              try {
+                                if (event.dataTransfer) {
+                                  event.dataTransfer.effectAllowed = 'copyMove';
+                                }
+                              } catch (error) {
+                                console.warn('[documents] Failed to configure drag effect', error);
+                              }
+                              writeTagTransferData(event.dataTransfer, tag, doc.id);
+                            }}
+                            onDragEnd={(event) => {
+                              event.stopPropagation();
+                            }}
+                            onKeyDown={clickable ? (event) => {
+                              if (event.key === 'Enter' || event.key === ' ') {
+                                event.preventDefault();
+                                event.stopPropagation();
+                                if (tagId == null) {
+                                  return;
+                                }
+                                onTagClick?.(tagId);
+                              }
+                            } : undefined}
+                          >
+                            {tag.label}
+                          </span>
+                        );
+                      })}
+                    </div>
+                  )}
+                </div>
+              </td>
+              <td>{issuedLabel}</td>
+              <td>{addedLabel}</td>
+            </tr>
+          );
+        })}
+      </tbody>
+    </table>
   );
 };
 
diff --git a/frontend/src/documents/DocumentsManager.ts b/frontend/src/documents/DocumentsManager.ts
index 357ad5f..d39711c 100644
--- a/frontend/src/documents/DocumentsManager.ts
+++ b/frontend/src/documents/DocumentsManager.ts
@@ -1,6 +1,5 @@
 import { shallowEqual } from 'react-redux';
-
-type DocumentId = string | number;
+import type { DocumentId } from '../types/identifiers';
 
 export type ManagedDocument = { id?: DocumentId | null } & Record<string, unknown>;
 
diff --git a/frontend/src/documents/SelectionAssignmentMenu.tsx b/frontend/src/documents/SelectionAssignmentMenu.tsx
index 3046c5f..bee9893 100644
--- a/frontend/src/documents/SelectionAssignmentMenu.tsx
+++ b/frontend/src/documents/SelectionAssignmentMenu.tsx
@@ -5,18 +5,18 @@ import { CheckIcon, CircleDashedCheckIcon, PlusIcon } from '../ui/icons';
 export type AssignmentState = 'all' | 'partial' | 'none';
 
 export interface SelectionAssignmentMenuItem {
-  id?: string | number;
+  id?: string;
   label?: string;
   state?: AssignmentState;
   count?: number | null;
   total?: number | null;
   color?: string | null;
-  value?: string | number;
+  value?: string;
   payload?: unknown;
 }
 
 export interface NormalizedSelectionAssignmentItem {
-  id: string | number;
+  id: string;
   label: string;
   state: AssignmentState;
   count: number | null;
@@ -105,7 +105,7 @@ const SelectionAssignmentMenu: React.FC<SelectionAssignmentMenuProps> = ({
   const inputRef = useRef<HTMLInputElement | null>(null);
   const [query, setQuery] = useState('');
   const [pending, setPending] = useState(false);
-  const [sortSnapshot, setSortSnapshot] = useState<Array<string | number> | null>(null);
+  const [sortSnapshot, setSortSnapshot] = useState<Array<string> | null>(null);
 
   const {
     isOpen,
@@ -175,10 +175,10 @@ const SelectionAssignmentMenu: React.FC<SelectionAssignmentMenuProps> = ({
 
   const orderedItems = useMemo(() => {
     if (freezeSortOnOpen && sortSnapshot && sortByState) {
-      const itemMap = new Map<string | number, NormalizedSelectionAssignmentItem>(
+      const itemMap = new Map<string, NormalizedSelectionAssignmentItem>(
         sortedByStateItems.map((item) => [item.id, item]),
       );
-      const seen = new Set<string | number>();
+      const seen = new Set<string>();
       const fromSnapshot = sortSnapshot
         .map((id) => {
           const entry = itemMap.get(id);
diff --git a/frontend/src/documents/SelectionFloatingActions.tsx b/frontend/src/documents/SelectionFloatingActions.tsx
index b4374e8..321035a 100644
--- a/frontend/src/documents/SelectionFloatingActions.tsx
+++ b/frontend/src/documents/SelectionFloatingActions.tsx
@@ -12,10 +12,10 @@ import SelectionAssignmentMenu, { SelectionAssignmentMenuItem } from './Selectio
 import SelectionSummary from './SelectionSummary';
 import { useAppState } from '../app/appState';
 import { useWorkspaceSelectionContext } from '../app/WorkspaceSelectionContext';
+import type { DocumentId } from '../types/identifiers';
 
 const ROOT_FOLDER_LABEL = 'Documents';
 
-type DocumentId = string | number;
 type NullableDocumentId = DocumentId | null;
 
 type SelectedIdList = NullableDocumentId[] | null;
@@ -145,7 +145,7 @@ const buildTagAssignments = (
     return [];
   }
 
-  const map = new Map<string | number, {
+  const map = new Map<string, {
     id?: DocumentId;
     label: string;
     color: string | null;
@@ -209,7 +209,7 @@ const buildCorrespondentAssignments = (
     return [];
   }
 
-  const map = new Map<string | number, {
+  const map = new Map<string, {
     id?: DocumentId;
     label: string;
     count: number;
@@ -491,7 +491,7 @@ const SelectionFloatingActions: React.FC<SelectionFloatingActionsProps> = ({
       const value = isRecord(candidate)
         ? (candidate?.id ?? candidate?.value ?? null)
         : candidate;
-      if (!value && value !== 0) {
+      if (!value) {
         return;
       }
       await onMoveDocumentsToFolder(documentIdList, value as DocumentId);
diff --git a/frontend/src/documents/context/DocumentsFilterContext.tsx b/frontend/src/documents/context/DocumentsFilterContext.tsx
index 618b683..706865e 100644
--- a/frontend/src/documents/context/DocumentsFilterContext.tsx
+++ b/frontend/src/documents/context/DocumentsFilterContext.tsx
@@ -1,10 +1,9 @@
 import React, { createContext, useContext } from 'react';
-
-type Identifier = string | number;
+import type { Identifier } from '../../types/identifiers';
 
 export interface DocumentsFilterValue {
   query: string;
-  searchResultIds: Array<string | number> | null;
+  searchResultIds: Array<string> | null;
   searchLoading: boolean;
   includeDescendants: boolean;
   activeTagIds: Identifier[];
diff --git a/frontend/src/documents/correspondents.ts b/frontend/src/documents/correspondents.ts
index 96f9fbc..8c5c0b5 100644
--- a/frontend/src/documents/correspondents.ts
+++ b/frontend/src/documents/correspondents.ts
@@ -1,5 +1,5 @@
 export interface CorrespondentReference {
-  id?: string | number | null;
+  id?: string | null;
   name?: string | null;
   key?: string;
 }
@@ -9,9 +9,9 @@ export interface DocumentLike {
 }
 
 export interface ResolvedCorrespondent {
-  id?: string | number | null;
+  id?: string | null;
   name: string;
-  key: string | number;
+  key: string;
 }
 
 export const resolveCorrespondents = (doc?: DocumentLike | null): ResolvedCorrespondent[] => {
@@ -19,7 +19,7 @@ export const resolveCorrespondents = (doc?: DocumentLike | null): ResolvedCorres
     return [];
   }
 
-  const seen = new Set<string | number>();
+  const seen = new Set<string>();
   const results: ResolvedCorrespondent[] = [];
 
   doc.correspondents.forEach((entry = {}, index) => {
diff --git a/frontend/src/documents/hooks/useBulkDocumentActions.ts b/frontend/src/documents/hooks/useBulkDocumentActions.ts
index 88ae110..374dbe6 100644
--- a/frontend/src/documents/hooks/useBulkDocumentActions.ts
+++ b/frontend/src/documents/hooks/useBulkDocumentActions.ts
@@ -1,7 +1,6 @@
 import { useCallback } from 'react';
 import { assignCorrespondentsBulk } from '../../lib/apiClient';
-
-export type Identifier = string | number;
+import type { Identifier } from '../../types/identifiers';
 
 type BulkAssignmentResponse = {
   assigned?: number;
@@ -62,35 +61,35 @@ const useBulkDocumentActions = ({
       if (!target?.id) {
         setStatusMessage('Unable to resolve correspondent.', 'error');
         return;
-    }
+      }
 
-    const response: BulkAssignmentResponse = await assignCorrespondentsBulk<BulkAssignmentResponse>({
-      document_ids: targets,
-      assignments: [
-        {
-          correspondent_id: target.id,
-        },
-      ],
-      action: 'add',
-    });
-
-    const { assigned = 0, removed = 0 } = response;
-
-    if (updateDocumentCaches && target.id) {
-      targets.forEach((docId) => {
-        updateDocumentCaches(docId, (doc) => {
-          if (!doc) return doc;
-          const current = Array.isArray((doc as any).correspondents) ? (doc as any).correspondents : [];
-          if (current.some((entry: any) => entry?.id === target.id)) {
-            return doc;
-          }
-          return {
-            ...(doc as any),
-            correspondents: [...current, { id: target.id, name: (target as any).name }],
-          };
-        });
+      const response: BulkAssignmentResponse = await assignCorrespondentsBulk<BulkAssignmentResponse>({
+        document_ids: targets,
+        assignments: [
+          {
+            correspondent_id: target.id,
+          },
+        ],
+        action: 'add',
       });
-    }
+
+      const { assigned = 0, removed = 0 } = response;
+
+      if (updateDocumentCaches && target.id) {
+        targets.forEach((docId) => {
+          updateDocumentCaches(docId, (doc) => {
+            if (!doc) return doc;
+            const current = Array.isArray((doc as any).correspondents) ? (doc as any).correspondents : [];
+            if (current.some((entry: any) => entry?.id === target.id)) {
+              return doc;
+            }
+            return {
+              ...(doc as any),
+              correspondents: [...current, { id: target.id, name: (target as any).name }],
+            };
+          });
+        });
+      }
       const assignedSuffix = assigned === 1 ? '' : 's';
       if (removed > 0) {
         const removedSuffix = removed === 1 ? '' : 's';
@@ -105,18 +104,18 @@ const useBulkDocumentActions = ({
         );
       }
 
-    if (input) {
-      input.value = '';
-    }
-  },
-  [
-    correspondentLookupByName,
-    handleCorrespondentCreate,
-    resolveTargetDocumentIds,
-    setStatusMessage,
-    updateDocumentCaches,
-  ],
-);
+      if (input) {
+        input.value = '';
+      }
+    },
+    [
+      correspondentLookupByName,
+      handleCorrespondentCreate,
+      resolveTargetDocumentIds,
+      setStatusMessage,
+      updateDocumentCaches,
+    ],
+  );
 
   const handleBulkCorrespondentRemove = useCallback(
     async ({ assignments = [], documentIds }: { assignments?: CorrespondentAssignment[]; documentIds?: Identifier[] }) => {
@@ -132,33 +131,33 @@ const useBulkDocumentActions = ({
         return;
       }
 
-    const normalizedAssignments = assignments.map((entry) => ({
-      correspondent_id: entry.correspondent_id,
-    }));
+      const normalizedAssignments = assignments.map((entry) => ({
+        correspondent_id: entry.correspondent_id,
+      }));
 
-    const response: BulkAssignmentResponse = await assignCorrespondentsBulk<BulkAssignmentResponse>({
-      document_ids: targets,
-      assignments: normalizedAssignments,
-      action: 'remove',
-    });
-
-    const { assigned = 0, removed = 0 } = response;
-    if (updateDocumentCaches) {
-      targets.forEach((docId) => {
-        updateDocumentCaches(docId, (doc) => {
-          if (!doc || !Array.isArray((doc as any).correspondents)) {
-            return doc;
-          }
-          const filtered = (doc as any).correspondents.filter(
-            (entry: any) =>
-              entry && !normalizedAssignments.some((assignment) => assignment.correspondent_id === entry.id),
-          );
-          return filtered.length === (doc as any).correspondents.length
-            ? doc
-            : { ...(doc as any), correspondents: filtered };
-        });
+      const response: BulkAssignmentResponse = await assignCorrespondentsBulk<BulkAssignmentResponse>({
+        document_ids: targets,
+        assignments: normalizedAssignments,
+        action: 'remove',
       });
-    }
+
+      const { assigned = 0, removed = 0 } = response;
+      if (updateDocumentCaches) {
+        targets.forEach((docId) => {
+          updateDocumentCaches(docId, (doc) => {
+            if (!doc || !Array.isArray((doc as any).correspondents)) {
+              return doc;
+            }
+            const filtered = (doc as any).correspondents.filter(
+              (entry: any) =>
+                entry && !normalizedAssignments.some((assignment) => assignment.correspondent_id === entry.id),
+            );
+            return filtered.length === (doc as any).correspondents.length
+              ? doc
+              : { ...(doc as any), correspondents: filtered };
+          });
+        });
+      }
 
       if (removed > 0) {
         const removedSuffix = removed === 1 ? '' : 's';
@@ -169,12 +168,12 @@ const useBulkDocumentActions = ({
       } else if (assigned > 0) {
         const assignedSuffix = assigned === 1 ? '' : 's';
         setStatusMessage(`Correspondent updated ${assigned} link${assignedSuffix}.`, 'info');
-    } else {
-      setStatusMessage('No correspondents changed.', 'info');
-    }
-  },
-  [resolveTargetDocumentIds, setStatusMessage, updateDocumentCaches],
-);
+      } else {
+        setStatusMessage('No correspondents changed.', 'info');
+      }
+    },
+    [resolveTargetDocumentIds, setStatusMessage, updateDocumentCaches],
+  );
 
   const handleDeleteSelection = useCallback(async () => {
     const docIds = Array.isArray(selectedDocumentIds) ? selectedDocumentIds : [];
diff --git a/frontend/src/documents/hooks/useDocumentsPanelProps.ts b/frontend/src/documents/hooks/useDocumentsPanelProps.ts
index 2112984..861526f 100644
--- a/frontend/src/documents/hooks/useDocumentsPanelProps.ts
+++ b/frontend/src/documents/hooks/useDocumentsPanelProps.ts
@@ -1,7 +1,6 @@
 import { useMemo } from 'react';
 import type { WorkspaceSelectionValue } from '../../app/WorkspaceSelectionContext';
-
-type Identifier = string | number;
+import type { Identifier } from '../../types/identifiers';
 
 interface DocumentLinkLike {
   url?: string | null;
@@ -96,8 +95,8 @@ const useDocumentsPanelProps = (props: UseDocumentsPanelPropsArgs) => {
     searchLoading,
     tagLookupById,
     activeCorrespondentFilters,
-  ensureAssetUrl,
-  getDocumentAsset,
+    ensureAssetUrl,
+    getDocumentAsset,
     handleDocumentTagDrop,
     documentsViewMode,
     documentsSortField,
diff --git a/frontend/src/documents/hooks/useDocumentsSelection.ts b/frontend/src/documents/hooks/useDocumentsSelection.ts
index 46c874d..6c7cfa1 100644
--- a/frontend/src/documents/hooks/useDocumentsSelection.ts
+++ b/frontend/src/documents/hooks/useDocumentsSelection.ts
@@ -1,20 +1,21 @@
 import { useCallback, useEffect, useMemo, useRef } from 'react';
 import { createDocumentEntryKey, createFolderEntryKey, isFolderEntry } from '../../app/entryKey';
+import type { DocumentId, FolderId } from '../../types/identifiers';
 
 interface FolderEntry {
-  id: string | number;
+  id: FolderId;
   [key: string]: unknown;
 }
 
 interface DocumentEntry {
-  id: string | number;
+  id: DocumentId;
   [key: string]: unknown;
 }
 
 interface NavigableRow {
   key: string;
   type: 'folder' | 'document';
-  id: string | number;
+  id: FolderId | DocumentId;
 }
 
 interface UseDocumentsSelectionOptions {
@@ -25,19 +26,19 @@ interface UseDocumentsSelectionOptions {
   visibleRowKeySet: Set<string>;
   selectedEntries: string[];
   selectionAnchorRef: { current: string | null };
-  promoteSelectionOrderRaw: (id: string | number) => void;
-  setFocusedDocumentId: (id: string | number | null) => void;
-  setActivePreviewId: (id: string | number | null) => void;
+  promoteSelectionOrderRaw: (id: DocumentId) => void;
+  setFocusedDocumentId: (id: DocumentId | null) => void;
+  setActivePreviewId: (id: DocumentId | null) => void;
   clearSelection: () => void;
-  focusedDocumentId: string | number | null;
+  focusedDocumentId: DocumentId | null;
   setFocusedRowKey: (value: string | null | ((current: string | null) => string | null)) => void;
   focusedRowKey: string | null;
 }
 
 const useDocumentsSelection = ({
   showingSearchResults,
-  currentSubfolders,
-  visibleDocuments,
+  currentSubfolders = [],
+  visibleDocuments = [],
   configureSelectionEnvironment,
   visibleRowKeySet,
   selectedEntries,
@@ -82,7 +83,7 @@ const useDocumentsSelection = ({
   }, [configureSelectionEnvironment, visibleRowKeySet, navigableRowKeys]);
 
   const promoteSelectionOrder = useCallback(
-    (docId: string | number | null) => {
+    (docId: DocumentId | null) => {
       if (!docId) return;
       promoteSelectionOrderRaw(docId);
       const rowKey = createDocumentEntryKey(docId);
@@ -99,7 +100,7 @@ const useDocumentsSelection = ({
     clearSelection();
   }, [clearSelection]);
 
-  const prevFocusedDocIdRef = useRef<string | number | null>(focusedDocumentId);
+  const prevFocusedDocIdRef = useRef<DocumentId | null>(focusedDocumentId);
   useEffect(() => {
     const previous = prevFocusedDocIdRef.current;
     if (previous === focusedDocumentId) {
@@ -109,7 +110,7 @@ const useDocumentsSelection = ({
     if (focusedDocumentId) {
       setFocusedRowKey(createDocumentEntryKey(focusedDocumentId));
     } else {
-      setFocusedRowKey((current) => (isFolderEntry(current) ? current : null));
+      setFocusedRowKey((current) => (current && isFolderEntry(current) ? current : null));
     }
   }, [focusedDocumentId, setFocusedRowKey]);
 
diff --git a/frontend/src/documents/panel/DocumentsPanel.tsx b/frontend/src/documents/panel/DocumentsPanel.tsx
index 175add7..2079f7d 100644
--- a/frontend/src/documents/panel/DocumentsPanel.tsx
+++ b/frontend/src/documents/panel/DocumentsPanel.tsx
@@ -18,6 +18,7 @@ import DocumentsPanelHeader, {
 import { SelectionFloatingPanel } from '../SelectionFloatingActions';
 import { createDocumentsTableHeaderActions } from './DocumentsToolbar';
 import { useDocumentsFilter } from '../context/DocumentsFilterContext';
+import type { Identifier } from '../../types/identifiers';
 
 const DEFAULT_GRID_ICON_SIZE = 144;
 
@@ -73,7 +74,7 @@ const DocumentsPanelInner: React.FC<DocumentsPanelInnerProps> = ({
   documentLinks,
   ensureDownloadUrl,
   deskWorkspaceProps = null,
-  onRefresh = () => {},
+  onRefresh = () => { },
   sortField,
   sortDirection,
   onSortFieldChange,
@@ -108,8 +109,8 @@ const DocumentsPanelInner: React.FC<DocumentsPanelInnerProps> = ({
     () =>
       Array.isArray(searchResultIds)
         ? searchResultIds
-            .map((id) => documentLookup?.get?.(id) || null)
-            .filter((doc): doc is Record<string, unknown> => Boolean(doc))
+          .map((id) => documentLookup?.get?.(id) || null)
+          .filter((doc): doc is Record<string, unknown> => Boolean(doc))
         : null,
     [searchResultIds, documentLookup],
   );
@@ -256,8 +257,7 @@ const DocumentsPanelInner: React.FC<DocumentsPanelInnerProps> = ({
   const isGridView = viewMode === 'grid';
   const isDeskView = viewMode === 'desk';
 
-  type Identifier = string | number;
-type ZoomSource = { url: string; alt?: string | null; mimeType?: string | null };
+  type ZoomSource = { url: string; alt?: string | null; mimeType?: string | null };
 
   const [previewDocId, setPreviewDocId] = useState<Identifier | null>(null);
 
@@ -499,7 +499,7 @@ type ZoomSource = { url: string; alt?: string | null; mimeType?: string | null }
       setFocusedRowKey(targetRow.key);
       handleEntrySelection(targetRow.key, {
         shiftKey,
-        preventDefault: () => {},
+        preventDefault: () => { },
       });
     },
     [
diff --git a/frontend/src/documents/panel/DocumentsPanelHeader.tsx b/frontend/src/documents/panel/DocumentsPanelHeader.tsx
index b58c73e..cae6b80 100644
--- a/frontend/src/documents/panel/DocumentsPanelHeader.tsx
+++ b/frontend/src/documents/panel/DocumentsPanelHeader.tsx
@@ -2,8 +2,7 @@ import React from 'react';
 import type { ReactNode } from 'react';
 import PanelHeader from '../../ui/PanelHeader';
 import BreadcrumbTrail from '../../ui/BreadcrumbTrail';
-
-type Identifier = string | number;
+import type { Identifier } from '../../types/identifiers';
 
 export interface DocumentsHeaderBreadcrumb {
   id?: Identifier;
@@ -40,12 +39,12 @@ const DocumentsPanelHeader: React.FC<DocumentsPanelHeaderProps> = ({
   const lastIndex = breadcrumbEntries.length - 1;
   const trailEntries = breadcrumbEntries.length
     ? breadcrumbEntries.map((crumb, index) => ({
-        id: crumb.id ?? index,
-        label: crumb.name ?? crumb.label ?? crumb.title ?? '',
-        onClick: index < lastIndex && onBreadcrumbClick
-          ? () => onBreadcrumbClick(crumb)
-          : null,
-      }))
+      id: crumb.id ?? index,
+      label: crumb.name ?? crumb.label ?? crumb.title ?? '',
+      onClick: index < lastIndex && onBreadcrumbClick
+        ? () => onBreadcrumbClick(crumb)
+        : null,
+    }))
     : [{ id: 'current-location', label: header.title }];
 
   const headerTitle = (
diff --git a/frontend/src/documents/tagTransfer.ts b/frontend/src/documents/tagTransfer.ts
index 9555ebd..5c74201 100644
--- a/frontend/src/documents/tagTransfer.ts
+++ b/frontend/src/documents/tagTransfer.ts
@@ -1,14 +1,16 @@
+import type { DocumentId, TagId } from '../types/identifiers';
+
 const TAG_MIME_TYPES = ['application/x-papercrate-tag', 'text/papercrate-tag'];
 const TAG_TEXT_MIME_TYPE = 'text/plain';
 
 interface TagPayload {
-  id: string | number;
+  id: TagId;
   label: string;
-  sourceDocId: string | number | null;
+  sourceDocId: DocumentId | null;
 }
 
 interface TagLike {
-  id?: string | number;
+  id?: TagId;
   label?: string | null;
 }
 
@@ -21,7 +23,10 @@ const serializePayload = (payload: TagPayload): string | null => {
   }
 };
 
-export const createTagTransferPayload = (tag?: TagLike | null, sourceDocId: string | number | null = null): TagPayload | null => {
+export const createTagTransferPayload = (
+  tag?: TagLike | null,
+  sourceDocId: DocumentId | null = null,
+): TagPayload | null => {
   if (!tag || tag.id == null) {
     return null;
   }
@@ -33,7 +38,11 @@ export const createTagTransferPayload = (tag?: TagLike | null, sourceDocId: stri
   };
 };
 
-export const writeTagTransferData = (dataTransfer: DataTransfer | null, tag: TagLike, sourceDocId: string | number | null = null): void => {
+export const writeTagTransferData = (
+  dataTransfer: DataTransfer | null,
+  tag: TagLike,
+  sourceDocId: DocumentId | null = null,
+): void => {
   if (!dataTransfer) {
     return;
   }
@@ -122,7 +131,7 @@ export const isTagTransferEvent = (event?: DragEventLike | null): boolean => {
   if (!types) {
     return false;
   }
-    const typeList = Array.isArray(types) ? [...types] : Array.from(types);
+  const typeList = Array.isArray(types) ? [...types] : Array.from(types);
   return TAG_MIME_TYPES.some((type) => typeList.includes(type));
 };
 
diff --git a/frontend/src/documents/useEntryPointer.ts b/frontend/src/documents/useEntryPointer.ts
index 35f3cdf..7e9451e 100644
--- a/frontend/src/documents/useEntryPointer.ts
+++ b/frontend/src/documents/useEntryPointer.ts
@@ -20,7 +20,7 @@ export const isPrimaryPointerEvent = (event?: PointerEventLike | null): boolean
 export type EntryType = 'document' | 'folder';
 
 export interface WorkspaceEntry {
-  id: string | number;
+  id: string;
   key?: string;
   type: EntryType;
   [key: string]: unknown;
@@ -28,7 +28,7 @@ export interface WorkspaceEntry {
 
 interface UseEntryPointerOptions {
   onSelectEntry?: (entry: WorkspaceEntry, event?: PointerEventLike | null, metadata?: EntryPointerMetadata) => void;
-  onDocumentActivate?: (id: string | number, metadata?: EntryPointerMetadata) => void;
+  onDocumentActivate?: (id: string, metadata?: EntryPointerMetadata) => void;
 }
 
 export interface EntryPointerMetadata {
@@ -36,7 +36,7 @@ export interface EntryPointerMetadata {
   primaryClick: boolean;
   rowKey: string;
   type: EntryType;
-  id: string | number;
+  id: string;
 }
 
 export const useEntryPointer = ({
diff --git a/frontend/src/documents/useInlineRename.ts b/frontend/src/documents/useInlineRename.ts
index d5863a2..e50293d 100644
--- a/frontend/src/documents/useInlineRename.ts
+++ b/frontend/src/documents/useInlineRename.ts
@@ -13,22 +13,22 @@ type FocusableInput = (HTMLInputElement | HTMLTextAreaElement) & {
 
 type InlineRenameOptions<TEntity> = {
   getCurrentValue?: (entity: TEntity) => string | null;
-  getEntityId?: (entity: TEntity) => string | number | null;
+  getEntityId?: (entity: TEntity) => string | null;
 };
 
 type InlineRenameHandler = (
-  id: string | number,
+  id: string,
   value: string,
 ) => boolean | void | Promise<boolean | void>;
 
 type InlineRenameReturn<TEntity> = {
-  editingId: string | number | null;
+  editingId: string | null;
   draftValue: string;
   setDraftValue: Dispatch<SetStateAction<string>>;
   beginEditing: (entity?: TEntity | null, event?: SyntheticEvent | Event) => void;
   cancelEditing: (event?: SyntheticEvent | Event) => void;
   submitEditing: (entity?: TEntity | null) => Promise<boolean>;
-  savingId: string | number | null;
+  savingId: string | null;
   attachInputRef: (node: FocusableInput | null) => void;
 };
 
@@ -51,18 +51,18 @@ const focusInput = (node: FocusableInput | null) => {
 const identity = (value: unknown) => value as string;
 
 const defaultGetEntityId = <T,>(entity?: T | null) =>
-  (entity as { id?: string | number } | null)?.id ?? null;
+  (entity as { id?: string } | null)?.id ?? null;
 
 const useInlineRename = <TEntity,>(
   onRename?: InlineRenameHandler,
   {
     getCurrentValue = identity as (entity: TEntity) => string | null,
-    getEntityId = defaultGetEntityId as (entity: TEntity) => string | number | null,
+    getEntityId = defaultGetEntityId as (entity: TEntity) => string | null,
   }: InlineRenameOptions<TEntity> = {},
 ): InlineRenameReturn<TEntity> => {
-  const [editingId, setEditingId] = useState<string | number | null>(null);
+  const [editingId, setEditingId] = useState<string | null>(null);
   const [draftValue, setDraftValue] = useState('');
-  const [savingId, setSavingId] = useState<string | number | null>(null);
+  const [savingId, setSavingId] = useState<string | null>(null);
   const inputRef = useRef<FocusableInput | null>(null);
 
   const resetState = useCallback(() => {
diff --git a/frontend/src/folders/FolderManagerContext.tsx b/frontend/src/folders/FolderManagerContext.tsx
index 85fcc83..e258b7c 100644
--- a/frontend/src/folders/FolderManagerContext.tsx
+++ b/frontend/src/folders/FolderManagerContext.tsx
@@ -17,7 +17,7 @@ const FolderManagerContext = createContext<FolderManager>(defaultManager);
 
 interface FolderManagerProviderProps {
   folderNodes?: Map<string | 'root', { name?: string | null }>;
-  ensureFolderData?: (folderId: string | 'root', options?: { force?: boolean; includeDocuments?: boolean }) => Promise<void>;
+  ensureFolderData?: (folderId: FolderId | 'root', options?: { force?: boolean; includeDocuments?: boolean }) => Promise<void>;
   children: ReactNode;
 }
 
diff --git a/frontend/src/hooks/documents/useCorrespondents.ts b/frontend/src/hooks/documents/useCorrespondents.ts
index 9a4541d..bbeb998 100644
--- a/frontend/src/hooks/documents/useCorrespondents.ts
+++ b/frontend/src/hooks/documents/useCorrespondents.ts
@@ -8,7 +8,7 @@ type ApiClient = {
 };
 
 interface CorrespondentEntry {
-  id?: string | number;
+  id?: string;
   name?: string;
   [key: string]: unknown;
 }
@@ -17,7 +17,7 @@ interface UseCorrespondentsOptions {
   apiClient: ApiClient;
   notifyApiError: (error: unknown, fallback: string) => void;
   setStatusMessage: (message: string, variant?: string) => void;
-  tenantIdRef: MutableRefObject<string | number | null>;
+  tenantIdRef: MutableRefObject<string | null>;
   mapDocumentCaches?: (mapper: (doc: any) => any) => void;
 }
 
@@ -47,7 +47,7 @@ const useCorrespondents = ({
   }, [apiClient, notifyApiError, tenantIdRef]);
 
   const handleCorrespondentUpdate = useCallback(
-    async (correspondentId: string | number, changes: { name?: string }) => {
+    async (correspondentId: string, changes: { name?: string }) => {
       if (correspondentId == null) {
         throw new Error('Missing correspondent identifier.');
       }
@@ -100,7 +100,7 @@ const useCorrespondents = ({
   );
 
   const handleCorrespondentDelete = useCallback(
-    async (correspondentId: string | number) => {
+    async (correspondentId: string) => {
       if (correspondentId == null) {
         throw new Error('Missing correspondent identifier.');
       }
diff --git a/frontend/src/hooks/documents/useDocumentCorrespondentActions.ts b/frontend/src/hooks/documents/useDocumentCorrespondentActions.ts
index 22267b3..c835cad 100644
--- a/frontend/src/hooks/documents/useDocumentCorrespondentActions.ts
+++ b/frontend/src/hooks/documents/useDocumentCorrespondentActions.ts
@@ -1,4 +1,5 @@
 import { useCallback, useMemo } from 'react';
+import type { Identifier } from '../../types/identifiers';
 
 
 type ApiClient = {
@@ -7,13 +8,11 @@ type ApiClient = {
 };
 
 interface CorrespondentOption {
-  id?: string | number;
+  id?: string;
   name?: string;
   [key: string]: unknown;
 }
 
-type Identifier = string | number;
-
 interface UseDocumentCorrespondentActionsArgs {
   apiClient: ApiClient;
   correspondents: CorrespondentOption[];
@@ -135,7 +134,7 @@ const useDocumentCorrespondentActions = ({
   };
 
   const handleCorrespondentAdd = useCallback(
-    async ({ document, name, input = null, option = null }: { document?: { id?: string | number }; name?: string; input?: HTMLInputElement | null; option?: CorrespondentOption | string | null }) => {
+    async ({ document, name, input = null, option = null }: { document?: { id?: string }; name?: string; input?: HTMLInputElement | null; option?: CorrespondentOption | string | null }) => {
       if (!document?.id) {
         throw new Error('Missing document for correspondent assignment.');
       }
diff --git a/frontend/src/hooks/documents/useDocumentDragHandlers.ts b/frontend/src/hooks/documents/useDocumentDragHandlers.ts
index d598466..ab9bd9c 100644
--- a/frontend/src/hooks/documents/useDocumentDragHandlers.ts
+++ b/frontend/src/hooks/documents/useDocumentDragHandlers.ts
@@ -1,9 +1,9 @@
 import { useCallback, useEffect, useMemo, useRef } from 'react';
 import type { DragEvent } from 'react';
 import { createDocumentEntryKey, createFolderEntryKey } from '../../app/entryKey';
+import type { FolderId, Identifier } from '../../types/identifiers';
 
-type Identifier = string | number;
-type FolderIdentifier = string | 'root';
+type FolderIdentifier = FolderId | 'root';
 type FolderInput = FolderIdentifier | number;
 
 interface DocumentLike {
@@ -14,7 +14,7 @@ interface DocumentLike {
 
 type ApplySelectionFn = (
   keys: string[],
-  options?: { anchor?: string | null; interactedKeys?: string[] },
+  options?: { anchor: string | null; interactedKeys?: string[] },
 ) => void;
 
 type HandleEntrySelectionFn = (
diff --git a/frontend/src/hooks/documents/useDocumentMutations.ts b/frontend/src/hooks/documents/useDocumentMutations.ts
index 2f333a2..713fbc4 100644
--- a/frontend/src/hooks/documents/useDocumentMutations.ts
+++ b/frontend/src/hooks/documents/useDocumentMutations.ts
@@ -13,9 +13,9 @@ import {
   trashDocument,
   updateDocument,
 } from '../../lib/apiClient';
+import type { DocumentId, FolderId as FolderIdentifier } from '../../types/identifiers';
 
-type DocumentId = string | number;
-type FolderId = DocumentId | 'root';
+type FolderId = FolderIdentifier | 'root';
 type NullableFolderId = FolderId | null;
 
 type StatusLevel = 'success' | 'error' | 'info' | string;
diff --git a/frontend/src/hooks/documents/useDocumentTagging.ts b/frontend/src/hooks/documents/useDocumentTagging.ts
index 404cb54..d01968c 100644
--- a/frontend/src/hooks/documents/useDocumentTagging.ts
+++ b/frontend/src/hooks/documents/useDocumentTagging.ts
@@ -1,6 +1,6 @@
 import { useCallback } from 'react';
 
-type Identifier = string | number;
+import type { Identifier } from '../../types/identifiers';
 
 interface TagRecord {
   id?: Identifier;
@@ -79,59 +79,59 @@ const useDocumentTagging = ({
       }
 
       try {
-      if (action === 'add') {
-        const createdIds: Identifier[] = [];
-        const createdTags: TagRecord[] = [];
-        for (const label of normalized) {
-          let tag = tags.find((item) => item.label.toLowerCase() === label.toLowerCase()) || null;
-          if (!tag) {
-            const payload = tagManager.buildPayload({ label });
-            const response = await apiClient.post<{ id?: Identifier; label: string }>('/tags', payload);
-            tag = 'data' in response ? response.data : response;
-            await refreshTags();
+        if (action === 'add') {
+          const createdIds: Identifier[] = [];
+          const createdTags: TagRecord[] = [];
+          for (const label of normalized) {
+            let tag = tags.find((item) => item.label.toLowerCase() === label.toLowerCase()) || null;
+            if (!tag) {
+              const payload = tagManager.buildPayload({ label });
+              const response = await apiClient.post<{ id?: Identifier; label: string }>('/tags', payload);
+              tag = 'data' in response ? response.data : response;
+              await refreshTags();
+            }
+            createdIds.push(tag.id);
+            createdTags.push(tag);
           }
-          createdIds.push(tag.id);
-          createdTags.push(tag);
-        }
-        tagIds = Array.from(new Set(createdIds));
+          tagIds = Array.from(new Set(createdIds));
 
-        if (updateDocumentCaches) {
-          const tagById = new Map<Identifier, TagRecord>();
-          tags.forEach((tag) => {
-            if (tag?.id != null) {
-              tagById.set(tag.id, tag);
-            }
-          });
-          createdTags.forEach((tag) => {
-            if (tag?.id != null) {
-              tagById.set(tag.id, tag);
-            }
-          });
-          targetDocumentIds.forEach((docId) => {
-            tagIds.forEach((tagId) => {
-              const cachedTag = tagById.get(tagId);
-              if (!cachedTag) {
-                return;
+          if (updateDocumentCaches) {
+            const tagById = new Map<Identifier, TagRecord>();
+            tags.forEach((tag) => {
+              if (tag?.id != null) {
+                tagById.set(tag.id, tag);
               }
-              updateDocumentCaches(docId, (doc) => {
-                if (!doc) {
-                  return doc;
+            });
+            createdTags.forEach((tag) => {
+              if (tag?.id != null) {
+                tagById.set(tag.id, tag);
+              }
+            });
+            targetDocumentIds.forEach((docId) => {
+              tagIds.forEach((tagId) => {
+                const cachedTag = tagById.get(tagId);
+                if (!cachedTag) {
+                  return;
                 }
-                const currentTags = Array.isArray((doc as any).tags) ? (doc as any).tags : [];
-                if (currentTags.some((entry: any) => entry?.id === tagId)) {
-                  return doc;
-                }
-                return {
-                  ...(doc as any),
-                  tags: [...currentTags, { ...cachedTag }],
-                };
+                updateDocumentCaches(docId, (doc) => {
+                  if (!doc) {
+                    return doc;
+                  }
+                  const currentTags = Array.isArray((doc as any).tags) ? (doc as any).tags : [];
+                  if (currentTags.some((entry: any) => entry?.id === tagId)) {
+                    return doc;
+                  }
+                  return {
+                    ...(doc as any),
+                    tags: [...currentTags, { ...cachedTag }],
+                  };
+                });
               });
             });
-          });
+          }
         }
-      }
 
-      tagIds = Array.from(new Set(tagIds));
+        tagIds = Array.from(new Set(tagIds));
 
         if (!tagIds.length) {
           return { ok: false, reason: 'no-tags' };
@@ -205,8 +205,7 @@ const useDocumentTagging = ({
       if (result?.ok) {
         const { tagCount, docsCount } = result;
         setStatusMessage(
-          `Assigned ${tagCount} tag${tagCount === 1 ? '' : 's'} to ${docsCount} document${
-            docsCount === 1 ? '' : 's'
+          `Assigned ${tagCount} tag${tagCount === 1 ? '' : 's'} to ${docsCount} document${docsCount === 1 ? '' : 's'
           }.`,
           'success',
         );
diff --git a/frontend/src/hooks/documents/useDocumentUploads.ts b/frontend/src/hooks/documents/useDocumentUploads.ts
index c4a3791..f239c74 100644
--- a/frontend/src/hooks/documents/useDocumentUploads.ts
+++ b/frontend/src/hooks/documents/useDocumentUploads.ts
@@ -3,8 +3,8 @@ import type { Dispatch, MutableRefObject, SetStateAction } from 'react';
 import useFileDrop from './useFileDrop';
 import { DEFAULT_FOLDER_NAME, hasFiles } from '../../app/workspaceUtils';
 import { fetchDocument } from '../../lib/apiClient';
+import type { Identifier } from '../../types/identifiers';
 
-type Identifier = string | number;
 type FolderId = Identifier | 'root' | null;
 
 type FileEntry = {
diff --git a/frontend/src/hooks/documents/useDocuments.ts b/frontend/src/hooks/documents/useDocuments.ts
index 8b82955..af8957e 100644
--- a/frontend/src/hooks/documents/useDocuments.ts
+++ b/frontend/src/hooks/documents/useDocuments.ts
@@ -7,8 +7,7 @@ import {
   useState,
 } from 'react';
 import DocumentsManager from '../../documents/DocumentsManager';
-
-type DocumentId = string | number;
+import type { DocumentId } from '../../types/identifiers';
 
 interface DocumentLike {
   id?: DocumentId;
diff --git a/frontend/src/hooks/documents/useDocumentsWorkspace.ts b/frontend/src/hooks/documents/useDocumentsWorkspace.ts
index 37fb461..95bd42b 100644
--- a/frontend/src/hooks/documents/useDocumentsWorkspace.ts
+++ b/frontend/src/hooks/documents/useDocumentsWorkspace.ts
@@ -52,6 +52,7 @@ import useWorkspaceTaxonomies from './useWorkspaceTaxonomies';
 import useWorkspaceBreadcrumbs from './useWorkspaceBreadcrumbs';
 import useWorkspaceDeskProps from './useWorkspaceDeskProps';
 import useWorkspaceSelectionSync from './useWorkspaceSelectionSync';
+import type { DocumentId, FolderId as FolderIdentifier, Identifier } from '../../types/identifiers';
 
 const EntryType = Object.freeze({
   document: 'document',
@@ -60,9 +61,7 @@ const EntryType = Object.freeze({
 
 const noop = () => { };
 
-type Identifier = string | number;
-type DocumentId = Identifier;
-type FolderId = Identifier | 'root';
+type FolderId = FolderIdentifier | 'root';
 
 interface DocumentLike {
   id?: DocumentId | null;
diff --git a/frontend/src/hooks/documents/useFileDrop.ts b/frontend/src/hooks/documents/useFileDrop.ts
index 8ab6a87..0b02fae 100644
--- a/frontend/src/hooks/documents/useFileDrop.ts
+++ b/frontend/src/hooks/documents/useFileDrop.ts
@@ -1,6 +1,6 @@
 import { MutableRefObject, useEffect } from 'react';
 
-type FolderId = string | number | 'root' | null;
+type FolderId = string | 'root' | null;
 
 interface DropOverlayState {
   active: boolean;
diff --git a/frontend/src/hooks/documents/useFolderTree.ts b/frontend/src/hooks/documents/useFolderTree.ts
index 7ac8dd4..b9b1e0e 100644
--- a/frontend/src/hooks/documents/useFolderTree.ts
+++ b/frontend/src/hooks/documents/useFolderTree.ts
@@ -8,9 +8,9 @@ import {
   createDocumentEntryKey,
   createFolderEntryKey,
 } from '../../app/entryKey';
+import type { FolderId as FolderIdentifier, Identifier } from '../../types/identifiers';
 
-type Identifier = string | number;
-type FolderId = Identifier | 'root';
+type FolderId = FolderIdentifier | 'root';
 
 interface DocumentLike {
   id?: Identifier | null;
@@ -126,8 +126,8 @@ const useFolderTree = ({
           .filter(Boolean),
       );
 
-      let nextDocKeys = [];
-      let mergedSelection = [];
+      let nextDocKeys: string[] = [];
+      let mergedSelection: string[] = [];
 
       setSelectedEntries((previous) => {
         const previousFolderKeys = previous
@@ -140,9 +140,11 @@ const useFolderTree = ({
       });
 
       const nextFocus = (() => {
-        const currentFocusedKey = createDocumentEntryKey(focusedDocumentId);
-        if (currentFocusedKey && availableDocKeySet.has(currentFocusedKey)) {
-          return focusedDocumentId;
+        if (focusedDocumentId) {
+          const currentFocusedKey = createDocumentEntryKey(focusedDocumentId);
+          if (currentFocusedKey && availableDocKeySet.has(currentFocusedKey)) {
+            return focusedDocumentId;
+          }
         }
         if (nextDocKeys.length) {
           const lastDocKey = nextDocKeys[nextDocKeys.length - 1];
@@ -172,7 +174,7 @@ const useFolderTree = ({
     if (!targetId || targetId === 'root') {
       setFolderNodes((prev: Map<FolderId, FolderTreeNode>) => {
         const root = prev.get('root');
-        if (root?.expanded) return prev;
+        if (!root || root.expanded) return prev;
         const next = new Map<FolderId, FolderTreeNode>(prev);
         next.set('root', { ...root, expanded: true });
         return next;
diff --git a/frontend/src/hooks/documents/useFolderTreeActions.ts b/frontend/src/hooks/documents/useFolderTreeActions.ts
index 781840b..96c2ff3 100644
--- a/frontend/src/hooks/documents/useFolderTreeActions.ts
+++ b/frontend/src/hooks/documents/useFolderTreeActions.ts
@@ -7,8 +7,8 @@ import {
   moveFolder as moveFolderRequest,
   renameFolder as renameFolderRequest,
 } from '../../lib/apiClient';
+import type { FolderId } from '../../types/identifiers';
 
-type FolderId = string | number;
 type FolderKey = FolderId | 'root';
 
 interface FolderNode {
diff --git a/frontend/src/hooks/documents/useTags.ts b/frontend/src/hooks/documents/useTags.ts
index b00e02d..815cef8 100644
--- a/frontend/src/hooks/documents/useTags.ts
+++ b/frontend/src/hooks/documents/useTags.ts
@@ -1,4 +1,5 @@
 import { MutableRefObject, useCallback, useState } from 'react';
+import type { TagId, TenantId } from '../../types/identifiers';
 
 type ApiClient = {
   get: (path: string) => Promise<{ data: unknown }>
@@ -12,7 +13,7 @@ interface TagManagerInterface {
 }
 
 interface TagEntry {
-  id?: string | number;
+  id?: TagId;
   label?: string;
   color?: string | null;
   [key: string]: unknown;
@@ -23,8 +24,8 @@ interface UseTagsOptions {
   notifyApiError: (error: unknown, fallback: string) => void;
   setStatusMessage: (message: string, variant?: string) => void;
   tagManager: TagManagerInterface;
-  tenantIdRef: MutableRefObject<string | number | null>;
-  setActiveTagFilters: (updater: (prev: Array<string | number>) => Array<string | number>) => void;
+  tenantIdRef: MutableRefObject<TenantId | null>;
+  setActiveTagFilters: (updater: (prev: Array<TagId>) => Array<TagId>) => void;
   mapDocumentCaches?: (mapper: (doc: any) => any) => void;
 }
 
@@ -56,7 +57,7 @@ const useTags = ({
   }, [apiClient, notifyApiError, tenantIdRef]);
 
   const handleTagUpdate = useCallback(
-    async (tagId: string | number, changes: { label?: string; color?: string | null }) => {
+    async (tagId: TagId, changes: { label?: string; color?: string | null }) => {
       if (tagId == null) {
         throw new Error('Missing tag identifier.');
       }
@@ -104,7 +105,7 @@ const useTags = ({
   );
 
   const handleTagDelete = useCallback(
-    async (tagId: string | number) => {
+    async (tagId: TagId) => {
       if (tagId == null) {
         throw new Error('Missing tag identifier.');
       }
diff --git a/frontend/src/hooks/documents/useTenantManager.ts b/frontend/src/hooks/documents/useTenantManager.ts
index 192e181..05766f0 100644
--- a/frontend/src/hooks/documents/useTenantManager.ts
+++ b/frontend/src/hooks/documents/useTenantManager.ts
@@ -1,5 +1,6 @@
 import { MutableRefObject, useCallback } from 'react';
 import type { NavigateFunction } from 'react-router-dom';
+import type { FolderId, TenantId } from '../../types/identifiers';
 
 interface ApiClient {
   get: (path: string) => Promise<{ data: unknown }>;
@@ -8,24 +9,24 @@ interface ApiClient {
 }
 
 interface TenantOption {
-  id?: string | number;
+  id?: TenantId;
   name?: string;
 }
 
 interface UseTenantManagerOptions {
   apiClient: ApiClient;
   appDispatch: (action: any) => void;
-  currentTenantId: string | number | null;
+  currentTenantId: TenantId | null;
   resetWorkspaceState: () => void;
   setStatusMessage: (message: string, variant?: string) => void;
   notifyApiError: (error: unknown, message: string) => void;
   refreshTags: () => Promise<void>;
   refreshCorrespondents: () => Promise<void>;
-  loadFolder: (folderId: string, options?: { preserveSearch?: boolean }) => Promise<void>;
+  loadFolder: (folderId: FolderId, options?: { preserveSearch?: boolean }) => Promise<void>;
   handleDocumentsViewModeChange: (mode: string) => void;
   navigate: NavigateFunction;
   tokenRef?: MutableRefObject<string | null>;
-  tenantIdRef?: MutableRefObject<string | number | null>;
+  tenantIdRef?: MutableRefObject<TenantId | null>;
 }
 
 const useTenantManager = ({
diff --git a/frontend/src/hooks/documents/useWorkspaceBreadcrumbs.ts b/frontend/src/hooks/documents/useWorkspaceBreadcrumbs.ts
index 9d422e2..060afdf 100644
--- a/frontend/src/hooks/documents/useWorkspaceBreadcrumbs.ts
+++ b/frontend/src/hooks/documents/useWorkspaceBreadcrumbs.ts
@@ -1,8 +1,8 @@
 import React, { useEffect, useMemo } from 'react';
 import { DEFAULT_FOLDER_NAME } from '../../app/workspaceUtils';
+import type { FolderId as FolderIdentifier } from '../../types/identifiers';
 
-type Identifier = string | number;
-type FolderId = Identifier | 'root';
+type FolderId = FolderIdentifier | 'root';
 
 interface UseWorkspaceBreadcrumbsArgs {
   selectedFolder: FolderId | null;
diff --git a/frontend/src/hooks/documents/useWorkspaceDeskProps.ts b/frontend/src/hooks/documents/useWorkspaceDeskProps.ts
index 3a37360..6fe6acb 100644
--- a/frontend/src/hooks/documents/useWorkspaceDeskProps.ts
+++ b/frontend/src/hooks/documents/useWorkspaceDeskProps.ts
@@ -1,11 +1,10 @@
 import { useCallback, useMemo } from 'react';
 import type { MutableRefObject } from 'react';
 import { createDocumentEntryKey } from '../../app/entryKey';
-
-type Identifier = string | number;
+import type { Identifier } from '../../types/identifiers';
 
 interface ApplySelectionFn {
-  (keys: string[], options?: { anchor?: string | null; interactedKeys?: string[] }): unknown;
+  (keys: string[], options?: { anchor: string | null; interactedKeys?: string[] }): unknown;
 }
 
 interface UseWorkspaceDeskPropsArgs {
@@ -17,8 +16,8 @@ interface UseWorkspaceDeskPropsArgs {
   applySelection: ApplySelectionFn;
   showingSearchResults: boolean;
   searchQuery: string;
-  activeTagFilters: Array<string | number>;
-  activeCorrespondentFilters: Array<string | number>;
+  activeTagFilters: Array<string>;
+  activeCorrespondentFilters: Array<string>;
   selectedFolder: Identifier | 'root' | null;
   promoteSelectionOrder: () => void;
   handleDocumentTagDrop: (docId: Identifier, tagId: Identifier) => Promise<void> | void;
diff --git a/frontend/src/hooks/documents/useWorkspaceSelectionSync.ts b/frontend/src/hooks/documents/useWorkspaceSelectionSync.ts
index 9f3236a..b3e2b15 100644
--- a/frontend/src/hooks/documents/useWorkspaceSelectionSync.ts
+++ b/frontend/src/hooks/documents/useWorkspaceSelectionSync.ts
@@ -1,14 +1,13 @@
 import { useEffect } from 'react';
 import type { MutableRefObject } from 'react';
-
-type Identifier = string | number;
+import type { Identifier } from '../../types/identifiers';
 
 interface UseWorkspaceSelectionSyncArgs {
   showingSearchResults: boolean;
   searchQuery: string;
-  setSelectedEntries: (entries: Array<string | number>) => void;
-  setSelectionOrder: (order: Array<string | number>) => void;
-  selectionOrderRef: MutableRefObject<Array<string | number>>;
+  setSelectedEntries: (entries: Array<string>) => void;
+  setSelectionOrder: (order: Array<string>) => void;
+  selectionOrderRef: MutableRefObject<Array<string>>;
   selectionAnchorRef: MutableRefObject<Identifier | string | null>;
   setFocusedDocumentId: (id: Identifier | null) => void;
   selectedDocumentIds: Identifier[];
diff --git a/frontend/src/hooks/documents/useWorkspaceTaxonomies.ts b/frontend/src/hooks/documents/useWorkspaceTaxonomies.ts
index f77756c..261aac1 100644
--- a/frontend/src/hooks/documents/useWorkspaceTaxonomies.ts
+++ b/frontend/src/hooks/documents/useWorkspaceTaxonomies.ts
@@ -5,8 +5,7 @@ import TagManager from '../../tag_manager';
 import useCorrespondents from './useCorrespondents';
 import useDocumentCorrespondentActions from './useDocumentCorrespondentActions';
 import useTags from './useTags';
-
-type Identifier = string | number;
+import type { Identifier } from '../../types/identifiers';
 
 interface UseWorkspaceTaxonomiesArgs {
   apiClient: any;
diff --git a/frontend/src/hooks/useAssetNavigator.ts b/frontend/src/hooks/useAssetNavigator.ts
index decf5de..112af21 100644
--- a/frontend/src/hooks/useAssetNavigator.ts
+++ b/frontend/src/hooks/useAssetNavigator.ts
@@ -1,7 +1,6 @@
 import { useEffect, useMemo, useState } from 'react';
 import { resolveAssetUrl } from '../asset_manager';
-
-type Identifier = string | number;
+import type { Identifier } from '../types/identifiers';
 
 type DocumentLike = {
   id?: Identifier;
@@ -27,7 +26,7 @@ type AssetLike = {
 type EnsureAssetUrl = (
   documentId: Identifier,
   asset: AssetLike,
-  options?: { force?: boolean; [key: string]: unknown },
+  options?: { force?: boolean;[key: string]: unknown },
 ) => Promise<unknown>;
 
 type GetAsset = (document: DocumentLike, assetType: string) => AssetLike | null;
@@ -92,7 +91,7 @@ export const useAssetNavigator = ({
     let cancelled = false;
     setIsLoading(true);
     ensureAssetUrl(documentId, asset, { force: true })
-      .catch(() => {})
+      .catch(() => { })
       .finally(() => {
         if (!cancelled) {
           setIsLoading(false);
diff --git a/frontend/src/lib/apiTypes.ts b/frontend/src/lib/apiTypes.ts
index 3c2638c..1abb117 100644
--- a/frontend/src/lib/apiTypes.ts
+++ b/frontend/src/lib/apiTypes.ts
@@ -1,6 +1,7 @@
 // Types aligned with OpenAPI schemas for common endpoints.
+import type { Identifier } from '../types/identifiers';
 
-export type Identifier = string | number;
+export type { Identifier };
 
 export interface DownloadLink {
   url: string;
diff --git a/frontend/src/login/LoginView.tsx b/frontend/src/login/LoginView.tsx
index 6ee1b44..3d5910a 100644
--- a/frontend/src/login/LoginView.tsx
+++ b/frontend/src/login/LoginView.tsx
@@ -12,7 +12,7 @@ const StatusBanner: React.FC<StatusBannerProps> = ({ status }) => {
 };
 
 interface TenantOption {
-  id?: string | number;
+  id?: string;
   name?: string;
 }
 
@@ -25,7 +25,7 @@ interface LoginViewProps {
   tenantSelection?: TenantSelectionState | null;
   onSelectTenant?: (tenant: TenantOption) => void;
   onCancelSelection?: () => void;
-  selectingTenantId?: string | number | null;
+  selectingTenantId?: string | null;
   onPasskeyLogin?: (username: string) => void;
   onSignup?: (username: string) => void;
   passkeySupported?: boolean;
@@ -88,88 +88,88 @@ const LoginView: React.FC<LoginViewProps> = ({
             <img
               src={loginLogoSrc}
               alt="Papercrate logo"
-            width={72}
-            height={72}
-            decoding="async"
-            loading="lazy"
-          />
-          <h1>Papercrate</h1>
-        </div>
-
-        <div className="login-card">
-          {hasTenantSelection ? (
-            <div className="login-card__selection">
-              <p>Select a tenant to finish signing in.</p>
-              <div className="login-card__tenant-list">
-                {tenantSelection?.tenants?.map((tenant) => (
-                <button
-                  key={tenant.id}
-                  type="button"
-                  onClick={() => onSelectTenant?.(tenant)}
-                  disabled={Boolean(selectingTenantId)}
-                  className={
-                    selectingTenantId === tenant.id
-                      ? 'login-card__tenant-button is-loading'
-                      : 'login-card__tenant-button'
-                  }
-                >
-                  {tenant.name}
-                </button>
-              ))}
-            </div>
-            <button
-              type="button"
-              className="login-card__back-button"
-              onClick={() => onCancelSelection?.()}
-              disabled={Boolean(selectingTenantId)}
-            >
-              Use a different account
-            </button>
+              width={72}
+              height={72}
+              decoding="async"
+              loading="lazy"
+            />
+            <h1>Papercrate</h1>
           </div>
-        ) : (
-          <>
-            <p>Use your registered passkey to sign in or create a new account.</p>
-            <form className="login-card__fields" onSubmit={handleSubmit}>
-              <label htmlFor="username">Username</label>
-              <input
-                id="username"
-                name="username"
-                value={username}
-                onChange={(event) => setUsername(event.target.value)}
-                placeholder="Username"
-                autoComplete="username"
-                disabled={passkeyLoading || magicLoginPending}
-                required
-              />
-              {passkeySupported ? (
+
+          <div className="login-card">
+            {hasTenantSelection ? (
+              <div className="login-card__selection">
+                <p>Select a tenant to finish signing in.</p>
+                <div className="login-card__tenant-list">
+                  {tenantSelection?.tenants?.map((tenant) => (
+                    <button
+                      key={tenant.id}
+                      type="button"
+                      onClick={() => onSelectTenant?.(tenant)}
+                      disabled={Boolean(selectingTenantId)}
+                      className={
+                        selectingTenantId === tenant.id
+                          ? 'login-card__tenant-button is-loading'
+                          : 'login-card__tenant-button'
+                      }
+                    >
+                      {tenant.name}
+                    </button>
+                  ))}
+                </div>
                 <button
-                  type="submit"
-                  className="login-card__passkey-button"
-                  disabled={passkeyLoading || magicLoginPending || !username.trim()}
+                  type="button"
+                  className="login-card__back-button"
+                  onClick={() => onCancelSelection?.()}
+                  disabled={Boolean(selectingTenantId)}
                 >
-                  {passkeyLoading ? 'Signing in…' : 'Sign in with passkey'}
+                  Use a different account
                 </button>
-              ) : (
-                <p className="settings-empty">Passkeys are not supported in this browser.</p>
-              )}
-            </form>
-            {signupSupported ? (
-              <button
-                type="button"
-                className="login-card__signup-button"
-                onClick={handleSignupClick}
-                disabled={signupLoading || magicLoginPending || !username.trim()}
-              >
-                {signupLoading ? 'Creating account…' : 'Create account with passkey'}
-              </button>
-            ) : null}
-          </>
-          )}
-          <StatusBanner status={status} />
+              </div>
+            ) : (
+              <>
+                <p>Use your registered passkey to sign in or create a new account.</p>
+                <form className="login-card__fields" onSubmit={handleSubmit}>
+                  <label htmlFor="username">Username</label>
+                  <input
+                    id="username"
+                    name="username"
+                    value={username}
+                    onChange={(event) => setUsername(event.target.value)}
+                    placeholder="Username"
+                    autoComplete="username"
+                    disabled={passkeyLoading || magicLoginPending}
+                    required
+                  />
+                  {passkeySupported ? (
+                    <button
+                      type="submit"
+                      className="login-card__passkey-button"
+                      disabled={passkeyLoading || magicLoginPending || !username.trim()}
+                    >
+                      {passkeyLoading ? 'Signing in…' : 'Sign in with passkey'}
+                    </button>
+                  ) : (
+                    <p className="settings-empty">Passkeys are not supported in this browser.</p>
+                  )}
+                </form>
+                {signupSupported ? (
+                  <button
+                    type="button"
+                    className="login-card__signup-button"
+                    onClick={handleSignupClick}
+                    disabled={signupLoading || magicLoginPending || !username.trim()}
+                  >
+                    {signupLoading ? 'Creating account…' : 'Create account with passkey'}
+                  </button>
+                ) : null}
+              </>
+            )}
+            <StatusBanner status={status} />
+          </div>
         </div>
       </div>
     </div>
-  </div>
   );
 };
 
diff --git a/frontend/src/preview/DocumentViewerLayout.tsx b/frontend/src/preview/DocumentViewerLayout.tsx
index b23f133..73760bd 100644
--- a/frontend/src/preview/DocumentViewerLayout.tsx
+++ b/frontend/src/preview/DocumentViewerLayout.tsx
@@ -5,7 +5,7 @@ import { DownloadIcon } from '../ui/icons';
 import PdfViewer from './PdfViewer';
 
 interface DocumentLike {
-  id?: string | number;
+  id?: string;
   title?: string;
   mime_type?: string;
   filename?: string;
@@ -40,7 +40,7 @@ interface DocumentViewerLayoutProps {
   summaryProps?: Record<string, unknown>;
   metadataPayload?: unknown;
   contentTabConfig?: ContentTabConfig | null;
-  resetKey?: string | number | null;
+  resetKey?: string | null;
   classNamePrefix?: string;
   defaultTabId?: string;
   infoPanelProps?: Record<string, unknown>;
@@ -211,12 +211,12 @@ const DocumentViewerLayout = ({
   const stackedLeadingTabs = useMemo(() => (
     isStacked
       ? [
-          {
-            id: 'preview',
-            label: 'Preview',
-            render: () => renderViewportPane(),
-          },
-        ]
+        {
+          id: 'preview',
+          label: 'Preview',
+          render: () => renderViewportPane(),
+        },
+      ]
       : []
   ), [isStacked, renderViewportPane]);
 
diff --git a/frontend/src/preview/DocumentViewerPanel.tsx b/frontend/src/preview/DocumentViewerPanel.tsx
index 3926ba6..287e8df 100644
--- a/frontend/src/preview/DocumentViewerPanel.tsx
+++ b/frontend/src/preview/DocumentViewerPanel.tsx
@@ -28,14 +28,15 @@ import BreadcrumbTrail from '../ui/BreadcrumbTrail';
 import DocumentViewerLayout from './DocumentViewerLayout';
 import useViewerLayoutMode from './useViewerLayoutMode';
 import { usePanelResizeBindings } from '../app/PanelManagerContext';
+import type { DocumentId, FolderId } from '../types/identifiers';
 
 interface DocumentLike {
-  id?: string | number;
+  id?: DocumentId;
   title?: string;
   mime_type?: string | null;
   issued_at?: string | null;
-  folder_id?: string | null;
-  correspondents?: Array<{ id?: string | number; name?: string }>;
+  folder_id?: FolderId | null;
+  correspondents?: Array<{ id?: string; name?: string }>;
   current_version?: {
     version_number?: number;
     download?: { url?: string | null; expires_at?: number } | null;
@@ -51,7 +52,7 @@ interface DocumentLike {
 }
 
 interface AssetLike {
-  id?: string | number;
+  id?: string;
   url?: string | null;
   metadata?: Record<string, unknown> | null;
   [key: string]: unknown;
@@ -59,16 +60,16 @@ interface AssetLike {
 
 interface DocumentViewerPanelProps extends DocumentSummarySectionProps {
   document: DocumentLike | null;
-  ensureAssetUrl?: (docId: string | number, asset: AssetLike, options?: { force?: boolean }) => Promise<unknown>;
+  ensureAssetUrl?: (docId: DocumentId, asset: AssetLike, options?: { force?: boolean }) => Promise<unknown>;
   getDocumentAsset?: (doc: DocumentLike | null, type: string) => AssetLike | null;
-  ensurePreviewData?: (docId: string | number, options?: { signal?: AbortSignal }) => Promise<DocumentLike | null>;
+  ensurePreviewData?: (docId: DocumentId, options?: { signal?: AbortSignal }) => Promise<DocumentLike | null>;
   notifyApiError?: (error: unknown, fallbackMessage?: string) => void;
   sidebarToggle?: ReactNode;
   onClosePanel?: () => void;
-  resolveFolderPath?: (doc: DocumentLike | null) => Array<{ id?: string | number; name?: string }>;
+  resolveFolderPath?: (doc: DocumentLike | null) => Array<{ id?: string; name?: string }>;
   variant?: 'viewer' | 'sidebar';
   onCollapsePanel?: () => void;
-  onMaximizePanel?: (args: { documentIds: Array<string | number> }) => void;
+  onMaximizePanel?: (args: { documentIds: Array<string> }) => void;
 }
 
 
@@ -163,7 +164,7 @@ const DocumentViewerPanel: React.FC<DocumentViewerPanelProps> = ({
   }, [document, getDocumentAsset]);
 
   const navigateToFolder = useCallback(
-    (folderId) => {
+    (folderId: FolderId | null) => {
       const target = folderId == null
         ? '/documents'
         : `/documents/folder/${folderId}`;
diff --git a/frontend/src/routes/DocumentViewerRoute.tsx b/frontend/src/routes/DocumentViewerRoute.tsx
index d03941e..4e6540e 100644
--- a/frontend/src/routes/DocumentViewerRoute.tsx
+++ b/frontend/src/routes/DocumentViewerRoute.tsx
@@ -2,8 +2,7 @@ import React, { useEffect } from 'react';
 import { Navigate, useNavigate, useParams } from 'react-router-dom';
 
 import { useAppShell } from '../appShellContext';
-
-type Identifier = string | number;
+import type { Identifier } from '../types/identifiers';
 
 interface DocumentViewerRouteContext {
   previewWorkspaceDocument?: { id?: Identifier } | null;
diff --git a/frontend/src/settings/components/CapabilityDropdown.tsx b/frontend/src/settings/components/CapabilityDropdown.tsx
index 0bf8841..29a0354 100644
--- a/frontend/src/settings/components/CapabilityDropdown.tsx
+++ b/frontend/src/settings/components/CapabilityDropdown.tsx
@@ -7,9 +7,7 @@ import {
 } from 'react';
 import type { JSX } from 'react';
 import { CheckIcon, ChevronDownIcon } from '../../ui/icons';
-
-
-type CapabilityValue = string | number;
+import type { CapabilityValue } from '../../types/identifiers';
 
 export interface CapabilityDropdownOption {
   value?: CapabilityValue | null;
diff --git a/frontend/src/settings/sections/ApiTokensSection.tsx b/frontend/src/settings/sections/ApiTokensSection.tsx
index d92bf58..0803b81 100644
--- a/frontend/src/settings/sections/ApiTokensSection.tsx
+++ b/frontend/src/settings/sections/ApiTokensSection.tsx
@@ -1,7 +1,6 @@
 import { useCallback, useEffect, useMemo, useState } from 'react';
 import type { ChangeEvent, FormEvent } from 'react';
-
-type Identifier = string | number;
+import type { Identifier } from '../../types/identifiers';
 
 interface ApiTokenEntry {
   id?: Identifier;
@@ -125,21 +124,21 @@ const ApiTokensSection = ({
   const capabilitySelectionOptions = useMemo<CapabilitySelectionOption[]>(() => (
     Array.isArray(capabilities)
       ? capabilities.map((capability) => {
-          const capabilityText = `${capability ?? ''}`;
-          if (!capabilityText.includes(':')) {
-            return { value: capability, label: capabilityText };
-          }
-          const [namespace, action] = capabilityText.split(':');
-          if (!namespace || !action) {
-            return { value: capability, label: capabilityText };
-          }
-          const formattedNamespace = `${namespace.charAt(0).toUpperCase()}${namespace.slice(1)}`;
-          const formattedAction = action.replace(/_/g, ' ');
-          return {
-            value: capability,
-            label: `${formattedNamespace}: ${formattedAction}`,
-          };
-        })
+        const capabilityText = `${capability ?? ''}`;
+        if (!capabilityText.includes(':')) {
+          return { value: capability, label: capabilityText };
+        }
+        const [namespace, action] = capabilityText.split(':');
+        if (!namespace || !action) {
+          return { value: capability, label: capabilityText };
+        }
+        const formattedNamespace = `${namespace.charAt(0).toUpperCase()}${namespace.slice(1)}`;
+        const formattedAction = action.replace(/_/g, ' ');
+        return {
+          value: capability,
+          label: `${formattedNamespace}: ${formattedAction}`,
+        };
+      })
       : []
   ), [capabilities]);
 
diff --git a/frontend/src/settings/sections/CapabilitySetsSection.tsx b/frontend/src/settings/sections/CapabilitySetsSection.tsx
index 0945db2..3806f14 100644
--- a/frontend/src/settings/sections/CapabilitySetsSection.tsx
+++ b/frontend/src/settings/sections/CapabilitySetsSection.tsx
@@ -8,10 +8,7 @@ import React, {
 import type { SettingsSectionConfig } from '../SettingsModal';
 import { IconX } from '../../ui/icons';
 import CapabilityDropdown, { CapabilityDropdownOption } from '../components/CapabilityDropdown';
-
-
-type CapabilityValue = string | number;
-type CapabilitySetId = string | number;
+import type { CapabilitySetId, CapabilityValue } from '../../types/identifiers';
 
 interface CapabilitySet {
   id: CapabilitySetId;
diff --git a/frontend/src/settings/sections/PasskeysSection.tsx b/frontend/src/settings/sections/PasskeysSection.tsx
index c773a7f..a3dee9f 100644
--- a/frontend/src/settings/sections/PasskeysSection.tsx
+++ b/frontend/src/settings/sections/PasskeysSection.tsx
@@ -18,10 +18,10 @@ interface PasskeysSectionProps {
   passkeysSupported?: boolean | null;
   passkeysLoading?: boolean;
   registeringPasskey?: boolean;
-  revokingPasskeyId?: string | number | null;
+  revokingPasskeyId?: string | null;
   onRefreshPasskeys?: () => void | Promise<void>;
   onRegisterPasskey?: (args: { nickname?: string }) => Promise<RegisterPasskeyResult | undefined>;
-  onRevokePasskey?: (id: string | number, reason?: string) => Promise<void>;
+  onRevokePasskey?: (id: string, reason?: string) => Promise<void>;
 }
 
 const PasskeysSection = ({
diff --git a/frontend/src/settings/useApiTokens.ts b/frontend/src/settings/useApiTokens.ts
index c950a9a..5e5e511 100644
--- a/frontend/src/settings/useApiTokens.ts
+++ b/frontend/src/settings/useApiTokens.ts
@@ -6,6 +6,7 @@ import {
   regenerateApiToken,
   type ApiTokenRecord,
 } from '../lib/apiClient';
+import type { ApiTokenId, CapabilitySetId } from '../types/identifiers';
 
 interface ApiTokensResponse {
   token_info?: ApiTokenRecord;
@@ -15,7 +16,7 @@ interface ApiTokensResponse {
 interface CreateTokenArgs {
   label?: string;
   expires_at?: string;
-  capability_set_id?: string | number;
+  capability_set_id?: CapabilitySetId;
 }
 
 interface UseApiTokensArgs {
@@ -28,13 +29,13 @@ interface UseApiTokensResult {
   tokens: ApiTokenRecord[];
   loading: boolean;
   creating: boolean;
-  deletingId: string | number | null;
-  regeneratingId: string | number | null;
+  deletingId: ApiTokenId | null;
+  regeneratingId: ApiTokenId | null;
   createdSecret: string | null;
   refresh: () => Promise<void>;
   create: (args?: CreateTokenArgs) => Promise<ApiTokensResponse | false>;
-  revoke: (tokenId?: string | number | null) => Promise<boolean>;
-  regenerate: (tokenId?: string | number | null) => Promise<boolean>;
+  revoke: (tokenId?: ApiTokenId | null) => Promise<boolean>;
+  regenerate: (tokenId?: ApiTokenId | null) => Promise<boolean>;
   dismissSecret: () => void;
 }
 
@@ -42,8 +43,8 @@ const useApiTokens = ({ notifyApiError, setStatusMessage, token }: UseApiTokensA
   const [tokens, setTokens] = useState<ApiTokenRecord[]>([]);
   const [loading] = useState(false);
   const [creating, setCreating] = useState(false);
-  const [deletingId, setDeletingId] = useState<string | number | null>(null);
-  const [regeneratingId, setRegeneratingId] = useState<string | number | null>(null);
+  const [deletingId, setDeletingId] = useState<ApiTokenId | null>(null);
+  const [regeneratingId, setRegeneratingId] = useState<ApiTokenId | null>(null);
   const [createdSecret, setCreatedSecret] = useState<string | null>(null);
 
   const refresh = useCallback(async () => {
@@ -65,7 +66,7 @@ const useApiTokens = ({ notifyApiError, setStatusMessage, token }: UseApiTokensA
       }
       setCreating(true);
       try {
-        const payload: { capability_set_id: string | number; label?: string; expires_at?: string } = { capability_set_id };
+        const payload: { capability_set_id: CapabilitySetId; label?: string; expires_at?: string } = { capability_set_id };
         if (label) {
           payload.label = label;
         }
@@ -100,7 +101,7 @@ const useApiTokens = ({ notifyApiError, setStatusMessage, token }: UseApiTokensA
   );
 
   const revoke = useCallback(
-    async (tokenId?: string | number | null) => {
+    async (tokenId?: string | null) => {
       if (!tokenId) {
         return false;
       }
@@ -121,7 +122,7 @@ const useApiTokens = ({ notifyApiError, setStatusMessage, token }: UseApiTokensA
   );
 
   const regenerate = useCallback(
-    async (tokenId?: string | number | null) => {
+    async (tokenId?: string | null) => {
       if (!tokenId) {
         return false;
       }
diff --git a/frontend/src/settings/useCapabilitySets.ts b/frontend/src/settings/useCapabilitySets.ts
index 5bef981..31dc014 100644
--- a/frontend/src/settings/useCapabilitySets.ts
+++ b/frontend/src/settings/useCapabilitySets.ts
@@ -5,8 +5,7 @@ import {
   listCapabilitySets,
   updateCapabilitySet as updateCapabilitySetRequest,
 } from '../lib/apiClient';
-
-type Identifier = string | number;
+import type { Identifier } from '../types/identifiers';
 
 interface CapabilitySet {
   id?: Identifier;
diff --git a/frontend/src/settings/usePasskeys.ts b/frontend/src/settings/usePasskeys.ts
index 18d0821..058178d 100644
--- a/frontend/src/settings/usePasskeys.ts
+++ b/frontend/src/settings/usePasskeys.ts
@@ -12,6 +12,7 @@ import {
   listPasskeys,
   startPasskeyRegistration,
 } from '../lib/apiClient';
+import type { PasskeyId } from '../types/identifiers';
 
 type StatusMessageFn = (message: string, variant?: string) => void;
 type NotifyApiErrorFn = (error: unknown, message: string) => void;
@@ -27,7 +28,7 @@ type ApiError = {
 };
 
 export interface PasskeyRecord {
-  id?: string | number;
+  id?: PasskeyId;
   nickname?: string;
   created_at?: string;
   createdAt?: string;
@@ -79,11 +80,11 @@ interface UsePasskeysResult {
   passkeysSupported: boolean | null;
   passkeysLoading: boolean;
   registeringPasskey: boolean;
-  revokingPasskeyId: string | number | null;
+  revokingPasskeyId: PasskeyId | null;
   refreshPasskeys: () => Promise<void>;
   registerPasskey: (options?: { nickname?: string }) => Promise<RegisterPasskeyResult>;
   revokePasskey: (
-    passkeyId: string | number,
+    passkeyId: PasskeyId,
     reason?: string,
   ) => Promise<RevokePasskeyResult>;
 }
@@ -93,7 +94,7 @@ const usePasskeys = ({ notifyApiError, setStatusMessage, token }: UsePasskeysArg
   const [passkeysSupported, setPasskeysSupported] = useState<boolean | null>(null);
   const [passkeysLoading, setPasskeysLoading] = useState(false);
   const [registeringPasskey, setRegisteringPasskey] = useState(false);
-  const [revokingPasskeyId, setRevokingPasskeyId] = useState<string | number | null>(null);
+  const [revokingPasskeyId, setRevokingPasskeyId] = useState<PasskeyId | null>(null);
 
   const refreshPasskeys = useCallback(async (): Promise<void> => {
     if (!token) {
@@ -191,7 +192,7 @@ const usePasskeys = ({ notifyApiError, setStatusMessage, token }: UsePasskeysArg
 
   const revokePasskey = useCallback(
     async (
-      passkeyId: string | number,
+      passkeyId: PasskeyId,
       reason?: string,
     ): Promise<RevokePasskeyResult> => {
       if (passkeyId == null) {
diff --git a/frontend/src/sidebar/Sidebar.tsx b/frontend/src/sidebar/Sidebar.tsx
index c3780f5..3cc0a91 100644
--- a/frontend/src/sidebar/Sidebar.tsx
+++ b/frontend/src/sidebar/Sidebar.tsx
@@ -31,6 +31,7 @@ import { getTagColorStyle } from '../utils/colors';
 import { useSidebarContext } from './SidebarContext';
 import { usePanelManager, usePanelResizeBindings } from '../app/PanelManagerContext';
 import type { StatusMessage } from '../hooks/documents/store/useDocumentsStore';
+import type { Identifier } from '../types/identifiers';
 
 interface CommunityLink {
   label: string;
@@ -60,7 +61,6 @@ const COMMUNITY_LINKS: CommunityLink[] = [
   },
 ];
 
-type Identifier = string | number;
 type FolderIdentifier = Identifier | 'root';
 
 interface FolderTreeNode {
@@ -528,94 +528,94 @@ const Sidebar: React.FC<SidebarProps> = ({
   const themeMenuSection =
     neutralHue != null
       ? (
-          <div className="menu__section">
-            <div className="menu__heading menu__heading--with-actions">
-              <span>Theme</span>
-              <div className="menu__heading-actions">
-                <button
-                  type="button"
-                  className="icon-button"
-                  onClick={handleThemeModeToggle}
-                  aria-label={`Switch theme (next: ${nextThemeLabel})`}
-                  title={`Theme: ${themeModeLabel} (next: ${nextThemeLabel})`}
-                >
-                  {themeModeIcon}
-                </button>
-                <button
-                  type="button"
-                  className="icon-button"
-                  onClick={handleThemeAdjustmentsReset}
-                  aria-label="Reset theme adjustments"
-                  title="Reset theme adjustments"
-                >
-                  <RestoreIcon size={16} />
-                </button>
-              </div>
+        <div className="menu__section">
+          <div className="menu__heading menu__heading--with-actions">
+            <span>Theme</span>
+            <div className="menu__heading-actions">
+              <button
+                type="button"
+                className="icon-button"
+                onClick={handleThemeModeToggle}
+                aria-label={`Switch theme (next: ${nextThemeLabel})`}
+                title={`Theme: ${themeModeLabel} (next: ${nextThemeLabel})`}
+              >
+                {themeModeIcon}
+              </button>
+              <button
+                type="button"
+                className="icon-button"
+                onClick={handleThemeAdjustmentsReset}
+                aria-label="Reset theme adjustments"
+                title="Reset theme adjustments"
+              >
+                <RestoreIcon size={16} />
+              </button>
             </div>
-            <label className="menu__slider" htmlFor={neutralHueInputId}>
-              <span className="menu__slider-label">Hue</span>
-              <input
-                id={neutralHueInputId}
-                type="range"
-                min="0"
-                max="360"
-                step="1"
-                value={neutralHue}
-                onChange={(event) => handleNeutralHueChange(event.target.value)}
-                onDoubleClick={resetNeutralHue}
-              />
-              <span className="menu__slider-value">{neutralHue}°</span>
-            </label>
-            <label className="menu__slider" htmlFor={neutralChromaInputId}>
-              <span className="menu__slider-label">Chroma</span>
-              <input
-                id={neutralChromaInputId}
-                type="range"
-                min="0"
-                max="1"
-                step="0.01"
-                value={neutralChroma}
-                onChange={(event) => handleNeutralChromaChange(event.target.value)}
-                onDoubleClick={resetNeutralChroma}
-              />
-              <span className="menu__slider-value">{formatSliderValue(neutralChroma)}</span>
-            </label>
-            <label className="menu__slider" htmlFor={neutralContrastInputId}>
-              <span className="menu__slider-label">Contrast</span>
-              <input
-                id={neutralContrastInputId}
-                type="range"
-                min="0"
-                max="1"
-                step="0.01"
-                value={neutralContrast}
-                onChange={(event) => handleNeutralContrastChange(event.target.value)}
-                onDoubleClick={resetNeutralContrast}
-              />
-              <span className="menu__slider-value">{formatSliderValue(neutralContrast)}</span>
-            </label>
           </div>
-        )
+          <label className="menu__slider" htmlFor={neutralHueInputId}>
+            <span className="menu__slider-label">Hue</span>
+            <input
+              id={neutralHueInputId}
+              type="range"
+              min="0"
+              max="360"
+              step="1"
+              value={neutralHue}
+              onChange={(event) => handleNeutralHueChange(event.target.value)}
+              onDoubleClick={resetNeutralHue}
+            />
+            <span className="menu__slider-value">{neutralHue}°</span>
+          </label>
+          <label className="menu__slider" htmlFor={neutralChromaInputId}>
+            <span className="menu__slider-label">Chroma</span>
+            <input
+              id={neutralChromaInputId}
+              type="range"
+              min="0"
+              max="1"
+              step="0.01"
+              value={neutralChroma}
+              onChange={(event) => handleNeutralChromaChange(event.target.value)}
+              onDoubleClick={resetNeutralChroma}
+            />
+            <span className="menu__slider-value">{formatSliderValue(neutralChroma)}</span>
+          </label>
+          <label className="menu__slider" htmlFor={neutralContrastInputId}>
+            <span className="menu__slider-label">Contrast</span>
+            <input
+              id={neutralContrastInputId}
+              type="range"
+              min="0"
+              max="1"
+              step="0.01"
+              value={neutralContrast}
+              onChange={(event) => handleNeutralContrastChange(event.target.value)}
+              onDoubleClick={resetNeutralContrast}
+            />
+            <span className="menu__slider-value">{formatSliderValue(neutralContrast)}</span>
+          </label>
+        </div>
+      )
       : null;
 
   const communityMenuFooter = COMMUNITY_LINKS.length
     ? (
-        <div className="menu__footer">
-          {COMMUNITY_LINKS.map(({ href, label, title, Icon }) => (
-            <a
-              key={href}
-              href={href}
-              target="_blank"
-              rel="noreferrer noopener"
-              className="menu__footer-link"
-              title={title}
-            >
-              <Icon size={16} stroke={1.5} />
-              <span>{label}</span>
-            </a>
-          ))}
-        </div>
-      )
+      <div className="menu__footer">
+        {COMMUNITY_LINKS.map(({ href, label, title, Icon }) => (
+          <a
+            key={href}
+            href={href}
+            target="_blank"
+            rel="noreferrer noopener"
+            className="menu__footer-link"
+            title={title}
+          >
+            <Icon size={16} stroke={1.5} />
+            <span>{label}</span>
+          </a>
+        ))}
+      </div>
+    )
     : null;
 
   const handleSearchInputChange = useCallback(
@@ -736,62 +736,62 @@ const Sidebar: React.FC<SidebarProps> = ({
   }
 
   const tenantMenuContent = tenantMenuOpen && tenantMenuStyle
-      ? createPortal(
-          <div
-            className={menuClassName}
-            ref={tenantMenuRef}
-            role="menu"
-            aria-label="Account menu"
-            style={tenantMenuStyle}
-          >
-            {showTenantList ? (
-              <div className="menu__section">
-                <div className="menu__heading">Switch tenant</div>
-                <div className="menu__wrapper">
-                  {tenants.map((tenant) => {
-                    const tenantId = tenant?.id || null;
-                    const isActive = tenantId === activeTenantId;
-                    const tenantLabel = tenant?.name || tenantId || 'Tenant';
-                    return (
-                      <button
-                        key={tenantId ?? tenantLabel}
-                        type="button"
-                        className={`menu__button${isActive ? ' active' : ''}`}
-                        onClick={() => handleTenantSelect(tenant)}
-                        role="menuitem"
-                      >
-                        <span className="menu__check-slot">
-                          {isActive ? <CheckIcon size={16} /> : null}
-                        </span>
-                        <span className="menu__label">{tenantLabel}</span>
-                      </button>
-                    );
-                  })}
-                </div>
-              </div>
-            ) : null}
-            <div className="menu__section">
-              <div className="menu__wrapper">
-                <button type="button" className="menu__button" onClick={handleSettingsFromMenu}>
-                  <SettingsIcon size={16} />
-                  Settings
-                </button>
-                <button
-                  type="button"
-                  className="menu__button menu__button--danger"
-                  onClick={handleLogoutFromMenu}
-                >
-                  <LogoutIcon size={16} />
-                  Log out
-                </button>
-              </div>
+    ? createPortal(
+      <div
+        className={menuClassName}
+        ref={tenantMenuRef}
+        role="menu"
+        aria-label="Account menu"
+        style={tenantMenuStyle}
+      >
+        {showTenantList ? (
+          <div className="menu__section">
+            <div className="menu__heading">Switch tenant</div>
+            <div className="menu__wrapper">
+              {tenants.map((tenant) => {
+                const tenantId = tenant?.id || null;
+                const isActive = tenantId === activeTenantId;
+                const tenantLabel = tenant?.name || tenantId || 'Tenant';
+                return (
+                  <button
+                    key={tenantId ?? tenantLabel}
+                    type="button"
+                    className={`menu__button${isActive ? ' active' : ''}`}
+                    onClick={() => handleTenantSelect(tenant)}
+                    role="menuitem"
+                  >
+                    <span className="menu__check-slot">
+                      {isActive ? <CheckIcon size={16} /> : null}
+                    </span>
+                    <span className="menu__label">{tenantLabel}</span>
+                  </button>
+                );
+              })}
             </div>
-            {themeMenuSection}
-            {communityMenuFooter}
-          </div>,
-          document.body,
-        )
-      : null;
+          </div>
+        ) : null}
+        <div className="menu__section">
+          <div className="menu__wrapper">
+            <button type="button" className="menu__button" onClick={handleSettingsFromMenu}>
+              <SettingsIcon size={16} />
+              Settings
+            </button>
+            <button
+              type="button"
+              className="menu__button menu__button--danger"
+              onClick={handleLogoutFromMenu}
+            >
+              <LogoutIcon size={16} />
+              Log out
+            </button>
+          </div>
+        </div>
+        {themeMenuSection}
+        {communityMenuFooter}
+      </div>,
+      document.body,
+    )
+    : null;
 
   return (
     <aside className={sidebarClassNames.join(' ')} ref={sidebarRef} style={sidebarStyle}>
@@ -925,9 +925,8 @@ const Sidebar: React.FC<SidebarProps> = ({
             </div>
           </div>
           <div
-            className={`sidebar-tag-cloud${
-              activeTagSet.size ? ' sidebar-tag-cloud--has-active' : ''
-            }`}
+            className={`sidebar-tag-cloud${activeTagSet.size ? ' sidebar-tag-cloud--has-active' : ''
+              }`}
             role="list"
           >
             {untaggedFilterId ? (
@@ -955,25 +954,25 @@ const Sidebar: React.FC<SidebarProps> = ({
                   style={style || undefined}
                   onClick={() => handleToggleTag(tag.id)}
                   aria-pressed={isActive}
-              draggable
-              onDragStart={(event) => {
-                try {
-                  const payload = JSON.stringify({
-                    id: tag.id,
-                    label: tag.label,
-                    color: tag.color || null,
-                  });
-                  event.dataTransfer.effectAllowed = 'copy';
-                  event.dataTransfer.setData('application/x-papercrate-tag', payload);
-                  event.dataTransfer.setData('text/papercrate-tag', payload);
-                } catch (error) {
-                  console.warn('[sidebar] Failed to set tag drag payload', error);
-                }
-              }}
-            >
-              {tag.label}
-            </button>
-          );
+                  draggable
+                  onDragStart={(event) => {
+                    try {
+                      const payload = JSON.stringify({
+                        id: tag.id,
+                        label: tag.label,
+                        color: tag.color || null,
+                      });
+                      event.dataTransfer.effectAllowed = 'copy';
+                      event.dataTransfer.setData('application/x-papercrate-tag', payload);
+                      event.dataTransfer.setData('text/papercrate-tag', payload);
+                    } catch (error) {
+                      console.warn('[sidebar] Failed to set tag drag payload', error);
+                    }
+                  }}
+                >
+                  {tag.label}
+                </button>
+              );
             })}
           </div>
         </div>
diff --git a/frontend/src/sidebar/useSidebarProps.ts b/frontend/src/sidebar/useSidebarProps.ts
index 2699f7d..125b4fd 100644
--- a/frontend/src/sidebar/useSidebarProps.ts
+++ b/frontend/src/sidebar/useSidebarProps.ts
@@ -2,8 +2,7 @@ import { useMemo } from 'react';
 import type { DragEvent } from 'react';
 import { TAG_FILTER_UNTAGGED } from '../app/workspaceUtils';
 import type { StatusMessage } from '../hooks/documents/store/useDocumentsStore';
-
-type Identifier = string | number;
+import type { Identifier } from '../types/identifiers';
 
 interface FolderTreeNode {
   id: Identifier;
diff --git a/frontend/src/types/identifiers.ts b/frontend/src/types/identifiers.ts
new file mode 100644
index 0000000..635b603
--- /dev/null
+++ b/frontend/src/types/identifiers.ts
@@ -0,0 +1,11 @@
+// Common string-based identifiers used across the app.
+export type Identifier = string;
+
+export type DocumentId = Identifier;
+export type FolderId = Identifier;
+export type CapabilitySetId = Identifier;
+export type CapabilityValue = Identifier;
+export type TenantId = Identifier;
+export type TagId = Identifier;
+export type ApiTokenId = Identifier;
+export type PasskeyId = Identifier;
diff --git a/frontend/src/ui/QuickAddMenu.tsx b/frontend/src/ui/QuickAddMenu.tsx
index f12d68e..e993557 100644
--- a/frontend/src/ui/QuickAddMenu.tsx
+++ b/frontend/src/ui/QuickAddMenu.tsx
@@ -4,10 +4,10 @@ import { PlusIcon } from './icons';
 
 import useFloatingMenu from './useFloatingMenu';
 
-type QuickAddOption = string | number | { id?: string | number; label?: string; name?: string;[key: string]: unknown };
+type QuickAddOption = string | { id?: string; label?: string; name?: string;[key: string]: unknown };
 
 interface NormalizedOption {
-  id?: string | number;
+  id?: string;
   label: string;
   original: QuickAddOption;
   index: number;
@@ -47,7 +47,7 @@ interface FloatingMenuState {
   updatePosition: () => void;
 }
 
-type CSSVarStyle = CSSProperties & Record<string, string | number>;
+type CSSVarStyle = CSSProperties & Record<string, string>;
 
 export interface QuickAddMenuProps {
   onSelectOption?: (value: QuickAddOption, normalized: NormalizedOption) => Promise<void> | void;
diff --git a/frontend/src/utils/date.ts b/frontend/src/utils/date.ts
index befd37f..ae09654 100644
--- a/frontend/src/utils/date.ts
+++ b/frontend/src/utils/date.ts
@@ -1,4 +1,4 @@
-const ensureDate = (value: string | number | Date | null): Date | null => {
+const ensureDate = (value: string | Date | null): Date | null => {
   if (!value) {
     return null;
   }
@@ -12,7 +12,7 @@ interface FormatOptions {
   options?: Intl.DateTimeFormatOptions;
 }
 
-export const formatDate = (value: string | number | Date | null, { fallback = '—', locale, options }: FormatOptions = {}): string => {
+export const formatDate = (value: string | Date | null, { fallback = '—', locale, options }: FormatOptions = {}): string => {
   const date = ensureDate(value);
   if (!date) {
     return fallback;
@@ -20,7 +20,7 @@ export const formatDate = (value: string | number | Date | null, { fallback = '
   return date.toLocaleDateString(locale, options);
 };
 
-export const formatDateTime = (value: string | number | Date | null, { fallback = '—', locale, options }: FormatOptions = {}): string => {
+export const formatDateTime = (value: string | Date | null, { fallback = '—', locale, options }: FormatOptions = {}): string => {
   const date = ensureDate(value);
   if (!date) {
     return fallback;
@@ -28,7 +28,7 @@ export const formatDateTime = (value: string | number | Date | null, { fallback
   return date.toLocaleString(locale, options);
 };
 
-export const toDateInputValue = (value: string | number | Date | null): string => {
+export const toDateInputValue = (value: string | Date | null): string => {
   const date = ensureDate(value);
   if (!date) {
     return '';
@@ -38,7 +38,7 @@ export const toDateInputValue = (value: string | number | Date | null): string =
   return localDate.toISOString().slice(0, 10);
 };
 
-export const toIssuedTimestamp = (dateString: string | null, fallback: string | number | Date | null): string | null => {
+export const toIssuedTimestamp = (dateString: string | null, fallback: string | Date | null): string | null => {
   if (!dateString) {
     return null;
   }
@@ -52,7 +52,7 @@ export const toIssuedTimestamp = (dateString: string | null, fallback: string |
   return Number.isNaN(candidate.getTime()) ? null : candidate.toISOString();
 };
 
-export const parseDateValue = (value: string | number | Date | null): Date | null => ensureDate(value);
+export const parseDateValue = (value: string | Date | null): Date | null => ensureDate(value);
 
 export default {
   formatDate,
diff --git a/frontend/src/utils/ocr.ts b/frontend/src/utils/ocr.ts
index c66b327..81b0d93 100644
--- a/frontend/src/utils/ocr.ts
+++ b/frontend/src/utils/ocr.ts
@@ -12,9 +12,9 @@ export interface DocumentLike extends AssetManagerDocumentLike {
 
 export type AssetLike = AssetManagerAssetLike;
 
-export type EnsurePreviewData = (id: string | number) => Promise<DocumentLike | null>;
+export type EnsurePreviewData = (id: string) => Promise<DocumentLike | null>;
 export type EnsureAssetUrl = (
-  id: string | number,
+  id: string,
   asset: AssetLike,
   options?: { force?: boolean },
 ) => Promise<AssetLike | null>;