diff --git a/frontend/src/correspondents/CorrespondentsPanel.jsx b/frontend/src/correspondents/CorrespondentsPanel.jsx
index 835705e..845090a 100644
--- a/frontend/src/correspondents/CorrespondentsPanel.jsx
+++ b/frontend/src/correspondents/CorrespondentsPanel.jsx
@@ -17,7 +17,7 @@ function CorrespondentsPanel({
 
   const startEdit = useCallback((correspondent) => {
     setEditingId(correspondent.id);
-    setDraftName(correspondent.name || '');
+    setDraftName(correspondent.name);
   }, []);
 
   const cancelEdit = useCallback(() => {
diff --git a/frontend/src/detail/DetailPanel.jsx b/frontend/src/detail/DetailPanel.jsx
index bdd71d2..88c7e9f 100644
--- a/frontend/src/detail/DetailPanel.jsx
+++ b/frontend/src/detail/DetailPanel.jsx
@@ -30,12 +30,9 @@ const derivePreviewOrientation = (metadata) => {
 
 const sortCorrespondents = (entries = []) =>
   entries
-    .map((entry) => ({
-      id: entry.id,
-      name: entry.name || '',
-      count: entry.count,
-    }))
-    .sort((a, b) => (a.name || '').localeCompare(b.name || ''));
+    .filter((entry) => entry && entry.name)
+    .map(({ id, name, count }) => ({ id, name, count }))
+    .sort((a, b) => a.name.localeCompare(b.name));
 
 const resolveDocumentType = (doc) => {
   if (!doc) {
@@ -46,15 +43,8 @@ const resolveDocumentType = (doc) => {
   if (!type) {
     return null;
   }
-  if (typeof type === 'string') {
-    const name = type.trim();
-    if (!name) {
-      return null;
-    }
-    return { id: fallbackId, name };
-  }
-  if (typeof type === 'object') {
-    const name = (type.name || type.label || '').trim();
+  if (typeof type === 'object' && typeof type.name === 'string') {
+    const name = type.name.trim();
     if (!name) {
       return null;
     }
@@ -265,7 +255,7 @@ const PreviewStack = ({
           >
             <img
               src={entry.url}
-              alt={entry.alt || ''}
+              alt={entry.alt}
               className="preview-stack__image"
               onClick={(event) => {
                 event.stopPropagation();
@@ -405,7 +395,7 @@ const DetailPanel = ({
   const startTitleEdit = useCallback(() => {
     if (!singleDoc) return;
     setTitleEditDocId(singleDoc.id);
-    setTitleDraft(singleDoc.title || singleDoc.original_name || '');
+    setTitleDraft(singleDoc.title || singleDoc.original_name);
     setTitleError(null);
   }, [singleDoc]);
 
@@ -576,14 +566,15 @@ const DetailPanel = ({
     const tagMap = new Map();
     selectedDocuments.forEach((doc) => {
       (doc.tags || []).forEach((tag) => {
-        const label = (tag?.label || '').trim();
+        if (!tag?.label) return;
+        const label = tag.label.trim();
         if (!label) return;
         if (!tagMap.has(label)) {
-          const fallback = tagLookupById.get(tag.id) || {};
+          const fallback = tagLookupById.get(tag.id);
           tagMap.set(label, {
             id: tag.id,
             label,
-            color: tag.color || fallback.color,
+            color: tag.color ?? fallback?.color ?? null,
           });
         }
       });
@@ -608,32 +599,42 @@ const DetailPanel = ({
 
   const correspondentOptions = useMemo(() => {
     const seen = new Set();
-    return availableCorrespondents
-      .map((entry) => (entry?.name || '').trim())
-      .filter((name) => {
-        if (!name) return false;
-        const lower = name.toLowerCase();
-        if (seen.has(lower)) {
-          return false;
-        }
-        seen.add(lower);
-        return true;
-      });
+    return availableCorrespondents.reduce((options, entry) => {
+      if (typeof entry?.name !== 'string') {
+        return options;
+      }
+      const name = entry.name.trim();
+      if (!name) {
+        return options;
+      }
+      const lower = name.toLowerCase();
+      if (seen.has(lower)) {
+        return options;
+      }
+      seen.add(lower);
+      options.push(name);
+      return options;
+    }, []);
   }, [availableCorrespondents]);
 
   const documentTypeOptions = useMemo(() => {
     const seen = new Set();
-    return (documentTypes || [])
-      .map((entry) => (entry?.name || '').trim())
-      .filter((name) => {
-        if (!name) return false;
-        const lower = name.toLowerCase();
-        if (seen.has(lower)) {
-          return false;
-        }
-        seen.add(lower);
-        return true;
-      });
+    return (documentTypes || []).reduce((options, entry) => {
+      if (typeof entry?.name !== 'string') {
+        return options;
+      }
+      const name = entry.name.trim();
+      if (!name) {
+        return options;
+      }
+      const lower = name.toLowerCase();
+      if (seen.has(lower)) {
+        return options;
+      }
+      seen.add(lower);
+      options.push(name);
+      return options;
+    }, []);
   }, [documentTypes]);
 
   const singleDocumentType = useMemo(() => resolveDocumentType(singleDoc), [singleDoc]);
@@ -751,11 +752,11 @@ const DetailPanel = ({
     selectedDocuments.forEach((doc) => {
       if (!doc?.id) return;
       (doc.correspondents || []).forEach((entry) => {
-        if (!entry?.id) return;
+        if (!entry?.id || typeof entry.name !== 'string') return;
         if (!map.has(entry.id)) {
           map.set(entry.id, {
             id: entry.id,
-            name: entry.name || '',
+            name: entry.name,
             documentIds: new Set(),
           });
         }
@@ -770,7 +771,7 @@ const DetailPanel = ({
         documentIds: [...entry.documentIds],
         count: entry.documentIds.size,
       }))
-      .sort((a, b) => (a.name || '').localeCompare(b.name || ''));
+      .sort((a, b) => a.name.localeCompare(b.name));
   }, [selectedDocuments]);
 
   const bulkDocumentTypes = useMemo(() => {
@@ -789,7 +790,7 @@ const DetailPanel = ({
       map.get(key).count += 1;
     });
 
-    return [...map.values()].sort((a, b) => (a.name || '').localeCompare(b.name || ''));
+    return [...map.values()].sort((a, b) => a.name.localeCompare(b.name));
   }, [selectedDocuments]);
 
   const bulkDocumentTypeSummary = useMemo(() => {
diff --git a/frontend/src/documentTypes/DocumentTypesPanel.jsx b/frontend/src/documentTypes/DocumentTypesPanel.jsx
index 8dd0557..c6cf54f 100644
--- a/frontend/src/documentTypes/DocumentTypesPanel.jsx
+++ b/frontend/src/documentTypes/DocumentTypesPanel.jsx
@@ -17,7 +17,7 @@ function DocumentTypesPanel({
 
   const startEdit = useCallback((entry) => {
     setEditingId(entry.id);
-    setDraftName(entry.name || '');
+    setDraftName(entry.name);
   }, []);
 
   const cancelEdit = useCallback(() => {
diff --git a/frontend/src/documents/DocumentsTable.jsx b/frontend/src/documents/DocumentsTable.jsx
index 83e9b8f..6098180 100644
--- a/frontend/src/documents/DocumentsTable.jsx
+++ b/frontend/src/documents/DocumentsTable.jsx
@@ -32,7 +32,7 @@ const resolveCorrespondents = (doc) => {
   const results = [];
 
   doc.correspondents.forEach((entry, index) => {
-    if (!entry) return;
+    if (!entry || typeof entry.name !== 'string') return;
 
     const id = entry.id;
     const name = entry.name.trim();
@@ -68,16 +68,8 @@ const resolveDocumentType = (doc) => {
     return null;
   }
 
-  if (typeof type === 'string') {
-    const name = type.trim();
-    if (!name) {
-      return null;
-    }
-    return { id: fallbackId, name };
-  }
-
-  if (typeof type === 'object') {
-    const name = (type.name || type.label || '').trim();
+  if (typeof type === 'object' && typeof type.name === 'string') {
+    const name = type.name.trim();
     if (!name) {
       return null;
     }
@@ -138,7 +130,7 @@ const DocumentThumbnailImage = ({
   document,
   ensureAssetUrl,
   getDocumentAsset,
-  alt,
+  alt = '',
   maxSize = LIST_ICON_SIZE,
   scrollRootRef = null,
 }) => {
@@ -210,7 +202,7 @@ const DocumentThumbnailImage = ({
         {url ? (
           <img
             src={url}
-            alt={alt || ''}
+            alt={alt}
             className="document-thumbnail"
             loading="lazy"
             decoding="async"
@@ -883,7 +875,7 @@ const DocumentsTable = ({
                                 aria-label={`Rename folder ${folder.name}`}
                                 onClick={(event) => {
                                   event.stopPropagation();
-                                  const nextName = window.prompt('Rename folder', folder.name || '');
+                                  const nextName = window.prompt('Rename folder', folder.name);
                                   if (!nextName) {
                                     return;
                                   }
diff --git a/frontend/src/documents/documentSummary.js b/frontend/src/documents/documentSummary.js
index 371cac1..66fb986 100644
--- a/frontend/src/documents/documentSummary.js
+++ b/frontend/src/documents/documentSummary.js
@@ -29,26 +29,14 @@ const sanitizeTags = (tags) => {
   if (!Array.isArray(tags)) {
     return [];
   }
-  return tags
-    .filter((tag) => tag && (tag.label || tag.id))
-    .map((tag) => ({
-      id: tag.id,
-      label: tag.label || '',
-      color: tag.color || null,
-    }));
+  return tags.filter((tag) => tag && (tag.label || tag.id));
 };
 
 const sanitizeCorrespondents = (entries) => {
   if (!Array.isArray(entries)) {
     return [];
   }
-  return entries
-    .filter((entry) => entry && (entry.name || entry.id))
-    .map((entry) => ({
-      id: entry.id,
-      name: entry.name || '',
-      count: entry.count,
-    }));
+  return entries.filter((entry) => entry && (entry.name || entry.id));
 };
 
 export const describeDocumentSummary = (document, options = {}) => {
@@ -76,8 +64,8 @@ export const describeDocumentSummary = (document, options = {}) => {
     formatDateTime = defaultFormatDateTime,
   } = options;
 
-  const title = document.title || '';
-  const originalName = document.original_name || '';
+  const title = document.title;
+  const originalName = document.original_name;
   const mimeTypeLabel = document.content_type || 'Unknown';
 
   const sizeBytes = Number(document.current_version?.size_bytes);
diff --git a/frontend/src/index.jsx b/frontend/src/index.jsx
index 8b0070d..6990eb6 100644
--- a/frontend/src/index.jsx
+++ b/frontend/src/index.jsx
@@ -55,7 +55,7 @@ const api = axios.create({
 });
 
 const storage = typeof window !== 'undefined' ? window.sessionStorage : undefined;
-const STORED_TOKEN = storage?.getItem('papercrate_token') || '';
+const STORED_TOKEN = storage?.getItem('papercrate_token') ?? '';
 let STORED_TENANT = null;
 if (storage) {
   try {
@@ -192,7 +192,7 @@ const AppStateProvider = ({ children }) => {
   const [state, dispatch] = useReducer(appStateReducer, initialAppState);
 
   useEffect(() => {
-    const token = state.token || '';
+    const token = state.token ?? '';
     if (token) {
       api.defaults.headers.common.Authorization = `Bearer ${token}`;
       storage?.setItem('papercrate_token', token);
@@ -1952,7 +1952,7 @@ const AppLayout = () => {
 
   const handleCorrespondentCreate = useCallback(
     async ({ name }) => {
-      const trimmed = (name || '').trim();
+      const trimmed = typeof name === 'string' ? name.trim() : '';
       if (!trimmed) {
         throw new Error('Correspondent name is required.');
       }
@@ -2073,7 +2073,7 @@ const AppLayout = () => {
       if (!document?.id) {
         throw new Error('Missing document for correspondent assignment.');
       }
-      const trimmed = (name || '').trim();
+      const trimmed = typeof name === 'string' ? name.trim() : '';
       if (!trimmed) {
         setStatusMessage('Correspondent name is required.', 'error');
         return;
@@ -2149,7 +2149,7 @@ const AppLayout = () => {
 
   const handleDocumentTypeCreate = useCallback(
     async ({ name }) => {
-      const trimmed = (name || '').trim();
+      const trimmed = typeof name === 'string' ? name.trim() : '';
       if (!trimmed) {
         throw new Error('Document type name is required.');
       }
@@ -2184,12 +2184,8 @@ const AppLayout = () => {
           }
 
           const existingType = doc.document_type;
-          const existingTypeId =
-            doc.document_type_id ?? (typeof existingType === 'object' ? existingType?.id : null);
-          const existingTypeName =
-            typeof existingType === 'string'
-              ? existingType
-              : existingType?.name || existingType?.label || '';
+          const existingTypeId = doc.document_type_id ?? existingType?.id ?? null;
+          const existingTypeName = typeof existingType?.name === 'string' ? existingType.name : undefined;
 
           const shouldClear =
             existingTypeId === documentTypeId ||
@@ -2223,7 +2219,7 @@ const AppLayout = () => {
   );
 
   const handleDocumentTypeAssign = useCallback(
-    async ({ documentId, documentTypeId }, { notify = true } = {}) => {
+    async ({ documentId, documentTypeId, documentType }, { notify = true } = {}) => {
       if (!documentId) {
         throw new Error('Missing document identifier.');
       }
@@ -2240,8 +2236,12 @@ const AppLayout = () => {
 
           const next = { ...doc };
           if (documentTypeId) {
-            const entry = documentTypeLookupById.get(documentTypeId);
-            next.document_type = entry || { id: documentTypeId, name: entry?.name || '' };
+            const entry =
+              documentTypeLookupById.get(documentTypeId) ||
+              (documentType?.name ? documentType : null);
+            next.document_type = entry
+              ? { id: entry.id ?? documentTypeId, name: entry.name }
+              : { id: documentTypeId, name: '' };
           } else {
             next.document_type = null;
           }
@@ -2282,7 +2282,7 @@ const AppLayout = () => {
       if (!document?.id) {
         throw new Error('Missing document for document type assignment.');
       }
-      const trimmed = (name || '').trim();
+      const trimmed = typeof name === 'string' ? name.trim() : '';
       if (!trimmed) {
         setStatusMessage('Document type name is required.', 'error');
         return;
@@ -2303,7 +2303,7 @@ const AppLayout = () => {
       }
 
       const success = await handleDocumentTypeAssign(
-        { documentId: document.id, documentTypeId: target.id },
+        { documentId: document.id, documentTypeId: target.id, documentType: target },
         { notify: true },
       );
 
@@ -2334,7 +2334,7 @@ const AppLayout = () => {
 
   const handleBulkDocumentTypeSet = useCallback(
     async ({ name, input, documentIds }) => {
-      const trimmed = (name || '').trim();
+      const trimmed = typeof name === 'string' ? name.trim() : '';
       if (!trimmed) {
         setStatusMessage('Document type name is required.', 'error');
         return;
@@ -2658,7 +2658,7 @@ const AppLayout = () => {
 
   const handleBulkCorrespondentAdd = useCallback(
     async ({ name, input, documentIds }) => {
-      const trimmed = (name || '').trim();
+      const trimmed = typeof name === 'string' ? name.trim() : '';
       if (!trimmed) {
         setStatusMessage('Correspondent name is required.', 'error');
         return;
@@ -2887,7 +2887,7 @@ const AppLayout = () => {
 
   const handleBulkTagAddFromDetail = useCallback(
     async ({ label, input, documentIds }) => {
-      const trimmed = (label || '').trim();
+      const trimmed = typeof label === 'string' ? label.trim() : '';
       if (!trimmed) {
         setStatusMessage('Enter a tag label.', 'error');
         return;
@@ -2920,7 +2920,7 @@ const AppLayout = () => {
 
   const handleBulkTagRemoveFromDetail = useCallback(
     async ({ label, input, documentIds }) => {
-      const trimmed = (label || '').trim();
+      const trimmed = typeof label === 'string' ? label.trim() : '';
       if (!trimmed) {
         setStatusMessage('Enter a tag label to remove.', 'error');
         return;
@@ -4190,7 +4190,7 @@ const AppLayout = () => {
         setStatusMessage('The root folder cannot be renamed.', 'error');
         return false;
       }
-      const trimmed = (nextName || '').trim();
+      const trimmed = typeof nextName === 'string' ? nextName.trim() : '';
       if (!trimmed) {
         setStatusMessage('Folder name cannot be empty.', 'error');
         return false;
@@ -6157,7 +6157,7 @@ const LoginRoute = () => {
 
   const handlePasskeyLogin = useCallback(
     async (rawUsername) => {
-      const username = (rawUsername || '').trim();
+      const username = typeof rawUsername === 'string' ? rawUsername.trim() : '';
       if (!username) {
         setStatusMessage('Enter your username before using a passkey.', 'error');
         return;
@@ -6238,7 +6238,7 @@ const LoginRoute = () => {
 
   const handleSignup = useCallback(
     async (rawUsername) => {
-      const username = (rawUsername || '').trim();
+      const username = typeof rawUsername === 'string' ? rawUsername.trim() : '';
       if (!username) {
         setStatusMessage('Choose a username to create your account.', 'error');
         return;
diff --git a/frontend/src/sidebar/Sidebar.jsx b/frontend/src/sidebar/Sidebar.jsx
index 9c91ec8..d113802 100644
--- a/frontend/src/sidebar/Sidebar.jsx
+++ b/frontend/src/sidebar/Sidebar.jsx
@@ -89,7 +89,7 @@ const FolderNode = ({
               onClick={(event) => {
                 event.stopPropagation();
                 if (!onRename) return;
-                const nextName = window.prompt('Rename folder', node.name || '');
+                const nextName = window.prompt('Rename folder', node.name);
                 if (!nextName) {
                   return;
                 }
@@ -174,24 +174,28 @@ const Sidebar = ({
   onSelectTenant,
   onOpenSettings,
 }) => {
-  const sortedCorrespondents = useMemo(
-    () =>
-      [...correspondents].sort((a, b) =>
-        (a?.name || '').localeCompare(b?.name || '', undefined, { sensitivity: 'base' }),
-      ),
-    [correspondents],
-  );
+  const sortedCorrespondents = useMemo(() => {
+    if (!Array.isArray(correspondents)) {
+      return [];
+    }
+    return correspondents
+      .filter((entry) => entry?.name)
+      .slice()
+      .sort((a, b) => a.name.localeCompare(b.name, undefined, { sensitivity: 'base' }));
+  }, [correspondents]);
   const activeCorrespondentSet = useMemo(
     () => new Set(activeCorrespondentIds || []),
     [activeCorrespondentIds],
   );
-  const sortedDocumentTypes = useMemo(
-    () =>
-      [...documentTypes].sort((a, b) =>
-        (a?.name || '').localeCompare(b?.name || '', undefined, { sensitivity: 'base' }),
-      ),
-    [documentTypes],
-  );
+  const sortedDocumentTypes = useMemo(() => {
+    if (!Array.isArray(documentTypes)) {
+      return [];
+    }
+    return documentTypes
+      .filter((entry) => entry?.name)
+      .slice()
+      .sort((a, b) => a.name.localeCompare(b.name, undefined, { sensitivity: 'base' }));
+  }, [documentTypes]);
   const activeDocumentTypeSet = useMemo(
     () => new Set(activeDocumentTypeIds || []),
     [activeDocumentTypeIds],
diff --git a/frontend/src/tags/TagsPanel.jsx b/frontend/src/tags/TagsPanel.jsx
index 0839e5b..2505ea7 100644
--- a/frontend/src/tags/TagsPanel.jsx
+++ b/frontend/src/tags/TagsPanel.jsx
@@ -24,8 +24,8 @@ function TagsPanel({
 
   const startEdit = useCallback((tag) => {
     setEditingId(tag.id);
-    setDraftLabel(tag.label || '');
-    setDraftColor(tag.color || '');
+    setDraftLabel(tag.label);
+    setDraftColor(tag.color ?? '');
   }, []);
 
   const cancelEdit = useCallback(() => {