diff --git a/frontend/src/app/PanelManagerContext.tsx b/frontend/src/app/PanelManagerContext.tsx
index af8123a..5198557 100644
--- a/frontend/src/app/PanelManagerContext.tsx
+++ b/frontend/src/app/PanelManagerContext.tsx
@@ -78,9 +78,6 @@ const persistWidth = (panel: PanelKey, value: number): void => {
 };
 
 const applyPanelWidthToRoot = (panel: PanelKey, width: number, active: boolean): void => {
-  if (!Number.isFinite(width)) {
-    return;
-  }
   const varName = panel === 'sidebar' ? '--sidebar-width' : '--detail-panel-width';
   const resolvedValue = panel === 'detail' && !active ? '0px' : `${width}px`;
   document.documentElement.style.setProperty(varName, resolvedValue);
@@ -170,9 +167,7 @@ export const PanelManagerProvider: React.FC<PanelManagerProviderProps> = ({ chil
   const setPanelWidth = useCallback(
     (panel: PanelKey, width: number, { commit = true, log = true }: SetPanelWidthOptions = {}) => {
       const clamped = clampPanelWidth(panel, width);
-      if (!Number.isFinite(clamped)) {
-        return panelWidthsRef.current[panel];
-      }
+
       if (panel === 'sidebar') {
         setSidebarWidthState((prev) => (prev === clamped ? prev : clamped));
       } else {
@@ -348,10 +343,7 @@ export const usePanelResizeBindings = (
       event.preventDefault();
       event.stopPropagation();
       const rect = panelRef.current.getBoundingClientRect();
-      const startWidth = Number.isFinite(rect?.width) ? rect.width : getPanelWidth(panel);
-      if (!Number.isFinite(startWidth)) {
-        return;
-      }
+      const startWidth = rect?.width ?? getPanelWidth(panel);
       const pointerId = event.pointerId ?? 'mouse';
       const startX = event.clientX;
       startPanelResize(panel);
@@ -398,9 +390,7 @@ export const usePanelResizeBindings = (
     ],
   );
 
-  const panelStyle = enabled && Number.isFinite(liveWidth)
-    ? { width: `${liveWidth}px` }
-    : undefined;
+  const panelStyle = enabled ? { width: `${liveWidth}px` } : undefined;
 
   const handleProps = enabled
     ? {
diff --git a/frontend/src/correspondents/CorrespondentsPanel.tsx b/frontend/src/correspondents/CorrespondentsPanel.tsx
index 91bf53b..80e7ce6 100644
--- a/frontend/src/correspondents/CorrespondentsPanel.tsx
+++ b/frontend/src/correspondents/CorrespondentsPanel.tsx
@@ -111,11 +111,7 @@ function CorrespondentsPanel({
   );
 
   const renderUsage = useCallback((correspondent: Correspondent) => {
-    const count = correspondent.usage_count;
-    if (count == null || !Number.isFinite(count)) {
-      return '0';
-    }
-    return count.toString();
+    return correspondent.usage_count;
   }, []);
 
   return (
diff --git a/frontend/src/desktop/hooks/usePreviewMetadata.ts b/frontend/src/desktop/hooks/usePreviewMetadata.ts
index 6cba541..4dd8ff2 100644
--- a/frontend/src/desktop/hooks/usePreviewMetadata.ts
+++ b/frontend/src/desktop/hooks/usePreviewMetadata.ts
@@ -1,8 +1,7 @@
 import { useEffect, useState, useRef } from 'react';
 import type { DocumentId } from '../../types/identifiers';
 import type { Document } from '../../types/documents';
-
-import type { Asset } from '../../types/assets';
+import type { Asset, ThumbnailMetadata } from '../../types/assets';
 
 interface PreviewMetadataEntry {
   docId: DocumentId;
@@ -40,13 +39,13 @@ const usePreviewMetadata = (
       const resolveAsset = (type: string) => getDocumentAsset?.(doc, type) ?? null;
 
       let asset = resolveAsset('thumbnail');
-      let metadata = (asset?.metadata as { width?: number; height?: number } | null) || null;
+      let metadata: Partial<ThumbnailMetadata> | null = (asset?.metadata as Partial<ThumbnailMetadata> | null) || null;
 
-      const hasDimensions = (meta: { width?: number | string; height?: number | string } | null) =>
-        Number.isFinite(Number(meta?.width)) &&
-        Number.isFinite(Number(meta?.height)) &&
-        Number(meta.width) > 0 &&
-        Number(meta.height) > 0;
+      const hasDimensions = (meta: Partial<ThumbnailMetadata> | null): meta is ThumbnailMetadata =>
+        typeof meta?.width === 'number' &&
+        typeof meta?.height === 'number' &&
+        meta.width > 0 &&
+        meta.height > 0;
 
       if (!hasDimensions(metadata) && ensureAssetUrl && docId && asset?.id) {
         // Skip if we already failed for this doc to avoid infinite loops
@@ -55,7 +54,7 @@ const usePreviewMetadata = (
             const ensured = await ensureAssetUrl(doc.id, asset);
             if (ensured) {
               asset = ensured;
-              metadata = (asset?.metadata as { width?: number; height?: number } | null) || null;
+              metadata = (asset?.metadata as Partial<ThumbnailMetadata> | null) || null;
             }
 
             // If still no dimensions, mark as failed so we don't try again
diff --git a/frontend/src/desktop/tags/useDeskTagInteractions.ts b/frontend/src/desktop/tags/useDeskTagInteractions.ts
index 27ac140..539254f 100644
--- a/frontend/src/desktop/tags/useDeskTagInteractions.ts
+++ b/frontend/src/desktop/tags/useDeskTagInteractions.ts
@@ -23,10 +23,8 @@ const createDragPreview = (node: EventTarget | null, clientX: number, clientY: n
         return null;
     }
     const rect = node.getBoundingClientRect();
-    const safeClientX = Number.isFinite(clientX) ? clientX : rect.left + rect.width / 2;
-    const safeClientY = Number.isFinite(clientY) ? clientY : rect.top + rect.height / 2;
-    const offsetX = Math.min(Math.max(safeClientX - rect.left, 0), rect.width);
-    const offsetY = Math.min(Math.max(safeClientY - rect.top, 0), rect.height);
+    const offsetX = Math.min(Math.max(clientX - rect.left, 0), rect.width);
+    const offsetY = Math.min(Math.max(clientY - rect.top, 0), rect.height);
     const clone = node.cloneNode(true) as HTMLElement;
     clone.style.position = 'absolute';
     clone.style.top = '-9999px';
diff --git a/frontend/src/documents/DocumentThumbnailImage.tsx b/frontend/src/documents/DocumentThumbnailImage.tsx
index 73649c4..fdaa282 100644
--- a/frontend/src/documents/DocumentThumbnailImage.tsx
+++ b/frontend/src/documents/DocumentThumbnailImage.tsx
@@ -67,9 +67,8 @@ const useLazyVisibility = (
 
 
 
-const getPageCount = (doc?: Document | null) => {
-  const count = doc?.current_version?.metadata?.page_count;
-  return Number.isFinite(count) ? Number(count) : null;
+const getPageCount = (doc?: Document | null): number | null => {
+  return doc?.current_version?.metadata?.page_count;
 };
 
 type Asset = AssetManagerAsset;
@@ -140,7 +139,7 @@ const DocumentThumbnailImage = ({
   }, [document, ensureAssetUrl, getDocumentAsset, isVisible, thumbnailAsset]);
 
   const pageCount = getPageCount(document);
-  const showMultiPageBadge = Number.isFinite(pageCount) && pageCount > 1;
+  const showMultiPageBadge = pageCount !== null && pageCount > 1;
   const innerClasses = ['document-thumbnail-inner'];
   if (showMultiPageBadge) {
     innerClasses.push('document-thumbnail-inner--multipage');
diff --git a/frontend/src/documents/SelectionAssignmentMenu.tsx b/frontend/src/documents/SelectionAssignmentMenu.tsx
index 59ec9be..edec50f 100644
--- a/frontend/src/documents/SelectionAssignmentMenu.tsx
+++ b/frontend/src/documents/SelectionAssignmentMenu.tsx
@@ -67,8 +67,8 @@ const normalizeItems = (items?: SelectionAssignmentMenuItem[]): NormalizedSelect
         : item.state === 'partial'
           ? 'partial'
           : 'none';
-      const numericCount = Number.isFinite(item.count) ? Number(item.count) : null;
-      const numericTotal = Number.isFinite(item.total) ? Number(item.total) : null;
+      const numericCount = item.count ?? null;
+      const numericTotal = item.total ?? null;
       return {
         id: item.id ?? trimmedLabel,
         label: trimmedLabel,
diff --git a/frontend/src/documents/documentSummary.ts b/frontend/src/documents/documentSummary.ts
index 648c3ca..5393288 100644
--- a/frontend/src/documents/documentSummary.ts
+++ b/frontend/src/documents/documentSummary.ts
@@ -25,7 +25,7 @@ const coercePageCount = (metadata?: { page_count?: number | string | null } | nu
     return null;
   }
   const parsed = Number.parseInt(String(raw), 10);
-  return Number.isFinite(parsed) && parsed >= 0 ? parsed : null;
+  return parsed >= 0 ? parsed : null;
 };
 
 const sanitizeArray = <T>(entries?: Array<T | null> | null): T[] =>
@@ -47,11 +47,11 @@ export const describeDocumentSummary = (document?: Document | null, options: Des
     return formatDateTime(value) || '—';
   };
   const doc = document ?? ({} as Document);
-  const sizeBytes = Number(doc.current_version?.size_bytes);
-  const sizeLabel = Number.isFinite(sizeBytes) && sizeBytes > 0 ? formatFileSize(sizeBytes) : '—';
+  const sizeBytes = doc.current_version?.size_bytes ?? null;
+  const sizeLabel = sizeBytes !== null && sizeBytes > 0 ? formatFileSize(sizeBytes) : '—';
   const metadata = doc.current_version?.metadata || null;
   const pageCount = coercePageCount(metadata);
-  const pageCountLabel = Number.isFinite(pageCount) ? String(pageCount) : '—';
+  const pageCountLabel = pageCount !== null ? String(pageCount) : '—';
   const folderLabel = doc.folder_id == null ? DEFAULT_FOLDER_NAME : `Folder ${doc.folder_id}`;
   const tags = sanitizeArray<DocumentTag>(doc.tags);
   const correspondents = sanitizeArray<DocumentCorrespondent>(doc.correspondents);
diff --git a/frontend/src/hooks/documents/useDocumentDragHandlers.ts b/frontend/src/hooks/documents/useDocumentDragHandlers.ts
index 7e17986..32be931 100644
--- a/frontend/src/hooks/documents/useDocumentDragHandlers.ts
+++ b/frontend/src/hooks/documents/useDocumentDragHandlers.ts
@@ -145,7 +145,7 @@ const useDocumentDragHandlers = ({
 
           let thumbWidth = size;
           let thumbHeight = size;
-          if (Number.isFinite(aspectRatio) && aspectRatio > 0) {
+          if (aspectRatio > 0) {
             if (aspectRatio >= 1) {
               thumbWidth = size;
               thumbHeight = Math.max(size / aspectRatio, size * 0.5);
diff --git a/frontend/src/hooks/documents/useDocumentTagging.ts b/frontend/src/hooks/documents/useDocumentTagging.ts
index d01968c..7dedd6f 100644
--- a/frontend/src/hooks/documents/useDocumentTagging.ts
+++ b/frontend/src/hooks/documents/useDocumentTagging.ts
@@ -267,7 +267,7 @@ const useDocumentTagging = ({
           },
         );
         const payload = 'data' in response ? response.data : response;
-        const queued = Number.isFinite(payload?.queued)
+        const queued = payload?.queued != null
           ? Number(payload.queued)
           : targetIds.length;
         setStatusMessage(
diff --git a/frontend/src/preview/PdfViewer.tsx b/frontend/src/preview/PdfViewer.tsx
index 1beec7a..e4730ad 100644
--- a/frontend/src/preview/PdfViewer.tsx
+++ b/frontend/src/preview/PdfViewer.tsx
@@ -519,7 +519,7 @@ const PdfViewer = ({ src, title, className, viewportRef }: PdfViewerProps): JSX.
             return;
           }
           const pageNumber = Number(attr);
-          if (!Number.isFinite(pageNumber) || pageNumber <= 0) {
+          if (!(pageNumber > 0)) {
             return;
           }
           handlePageVisibilityChange(pageNumber, entry.isIntersecting);
@@ -833,15 +833,6 @@ function PdfPageCanvas({
     const safePageHeight = Math.max(1, descriptor.height);
     const widthScale = safeViewportWidth / safePageWidth;
     const heightScale = safeViewportHeight / safePageHeight;
-    if (!Number.isFinite(widthScale) && Number.isFinite(heightScale)) {
-      return 'height';
-    }
-    if (!Number.isFinite(heightScale) && Number.isFinite(widthScale)) {
-      return 'width';
-    }
-    if (!Number.isFinite(widthScale) && !Number.isFinite(heightScale)) {
-      return 'width';
-    }
     return widthScale <= heightScale ? 'width' : 'height';
   }, [descriptor.height, descriptor.width, viewMode, viewportHeight, viewportWidth]);
 
diff --git a/frontend/src/settings/sections/CapabilitySetsSection.tsx b/frontend/src/settings/sections/CapabilitySetsSection.tsx
index f88174c..479a4ef 100644
--- a/frontend/src/settings/sections/CapabilitySetsSection.tsx
+++ b/frontend/src/settings/sections/CapabilitySetsSection.tsx
@@ -161,7 +161,7 @@ const CapabilitySetsSection: React.FC<CapabilitySetsSectionProps> = ({
       label: set.label || set.slug || set.id,
       capabilities: Array.isArray(set.capabilities) ? set.capabilities : [],
       isSystem: Boolean(set?.is_system),
-      version: Number.isFinite(set?.cap_version) ? Number(set.cap_version) : null,
+      version: set?.cap_version != null ? Number(set.cap_version) : null,
     })),
     [capabilitySets],
   );
@@ -492,7 +492,7 @@ const CapabilitySetsSection: React.FC<CapabilitySetsSectionProps> = ({
                         : '—'}
                     </td>
                     <td>{isSystem ? 'Yes' : 'No'}</td>
-                    <td>{Number.isFinite(set.cap_version) ? Number(set.cap_version) : '—'}</td>
+                    <td>{set.cap_version != null ? Number(set.cap_version) : '—'}</td>
                     <td className="settings-table__actions">
                       {isSystem ? (
                         <span className="settings-status">System set</span>
diff --git a/frontend/src/types/assets.ts b/frontend/src/types/assets.ts
index 9e637bc..18d16a2 100644
--- a/frontend/src/types/assets.ts
+++ b/frontend/src/types/assets.ts
@@ -1,10 +1,15 @@
 import type { Identifier } from './identifiers';
 import type { Download } from './common';
 
+export interface ThumbnailMetadata {
+    width: number;
+    height: number;
+}
+
 export interface Asset {
     id?: Identifier;
     asset_type?: string;
     download?: Download | null;
-    metadata?: Record<string, unknown> | null;
+    metadata?: ThumbnailMetadata | Record<string, unknown> | null;
     [key: string]: unknown;
 }
diff --git a/frontend/src/types/documents.ts b/frontend/src/types/documents.ts
index f5a8f06..5094997 100644
--- a/frontend/src/types/documents.ts
+++ b/frontend/src/types/documents.ts
@@ -40,7 +40,7 @@ export interface Correspondent {
 export interface DocumentVersion {
     assets?: Record<string, Asset> | Asset[] | null;
     metadata?: Record<string, unknown> & { page_count?: number } | null;
-    size_bytes?: number | string | null;
+    size_bytes?: number | null;
     checksum?: string | null;
     download?: Download | null;
     [key: string]: unknown;
diff --git a/frontend/src/ui/icons.tsx b/frontend/src/ui/icons.tsx
index 51c7a43..2fc6ebc 100644
--- a/frontend/src/ui/icons.tsx
+++ b/frontend/src/ui/icons.tsx
@@ -123,11 +123,11 @@ export const CorrespondentIcon = createIcon(IconUserFilled, { baseClass: 'icon i
 
 // Custom icons that need special handling
 export const FolderIcon: TablerIconComponent = ({ className, size = 16, title, ...rest }) => {
-  const dimensionProps = Number.isFinite(size) ? { width: Number(size), height: Number(size) } : {};
   return (
     <FolderSvg
       className={composeClassName('folder-icon', className)}
-      {...dimensionProps}
+      width={size}
+      height={size}
       role={title ? 'img' : 'presentation'}
       aria-hidden={title ? undefined : true}
       focusable="false"
diff --git a/frontend/src/ui/useFloatingMenu.ts b/frontend/src/ui/useFloatingMenu.ts
index e359611..8322ba3 100644
--- a/frontend/src/ui/useFloatingMenu.ts
+++ b/frontend/src/ui/useFloatingMenu.ts
@@ -33,8 +33,8 @@ const formatStyle = (metrics: FloatingMenuMetrics | null): FloatingMenuStyle =>
     top: metrics.top,
     left: metrics.left,
   };
-  if (Number.isFinite(metrics.minWidth)) {
-    style['--floating-min-width'] = `${Math.max(metrics.minWidth ?? 0, 0)}px`;
+  if (metrics.minWidth != null) {
+    style['--floating-min-width'] = `${Math.max(metrics.minWidth, 0)}px`;
   }
   if (metrics.width) {
     style.width = metrics.width;
diff --git a/frontend/src/utils/format.ts b/frontend/src/utils/format.ts
index 556b244..e7be327 100644
--- a/frontend/src/utils/format.ts
+++ b/frontend/src/utils/format.ts
@@ -1,17 +1,14 @@
-export const formatFileSize = (value: number | string): string => {
-  const bytes = Number(value);
-  if (!Number.isFinite(bytes) || bytes <= 0) {
-    return '0 B';
-  }
-
+export const formatFileSize = (bytes: number): string => {
+  const sign = bytes < 0 ? '-' : '';
   const units = ['B', 'KiB', 'MiB', 'GiB', 'TiB', 'PiB'];
   let index = 0;
-  let amount = bytes;
+  let amount = Math.abs(bytes);
 
   while (amount >= 1024 && index < units.length - 1) {
     amount /= 1024;
     index += 1;
   }
 
-  return `${amount.toFixed(2)} ${units[index]}`;
+  const decimals = index === 0 ? 0 : 2;
+  return `${sign}${amount.toFixed(decimals)} ${units[index]}`;
 };