diff --git a/Makefile b/Makefile
index fe488509..239572d1 100644
--- a/Makefile
+++ b/Makefile
@@ -220,7 +220,7 @@ deps:
 
 # Build for production
 build-prod:
-	VERSION=$${VERSION:-unknown}; \
+	VERSION=$${VERSION:-$$(git describe --tags --abbrev=0 2>/dev/null || echo "unknown")}; \
 	COMMIT_ID=$${COMMIT_ID:-unknown}; \
 	BUILD_TIME=$${BUILD_TIME:-unknown}; \
 	GO_VERSION=$${GO_VERSION:-unknown}; \
diff --git a/frontend/src/i18n/locales/en-US.ts b/frontend/src/i18n/locales/en-US.ts
index 337f3f4e..4e4b7855 100755
--- a/frontend/src/i18n/locales/en-US.ts
+++ b/frontend/src/i18n/locales/en-US.ts
@@ -1114,6 +1114,7 @@ export default {
       questionIndexModeDescription: 'Combined: Standard and similar questions are indexed together. Separate: Each question is indexed independently for more precise retrieval but requires more storage.',
       entryGuide: 'Each FAQ entry contains a primary question, similar questions, negative examples, and multiple answers. Manage them in the FAQ knowledge base detail view.',
       tagDesc: 'Select category for FAQ entries',
+      tagPlaceholder: 'Please select a category',
       modes: {
         questionOnly: 'Questions only',
         questionAnswer: 'Question + answer',
diff --git a/frontend/src/i18n/locales/ko-KR.ts b/frontend/src/i18n/locales/ko-KR.ts
index 626d9857..5dbec7bf 100755
--- a/frontend/src/i18n/locales/ko-KR.ts
+++ b/frontend/src/i18n/locales/ko-KR.ts
@@ -1238,6 +1238,7 @@ export default {
       questionIndexModeDescription: "병합 인덱스: 표준 질문과 유사 질문을 병합 인덱싱; 개별 인덱스: 표준 질문과 각 유사 질문을 독립적으로 인덱싱하여 더 정확하게 검색하지만 더 많은 저장 공간이 필요합니다",
       entryGuide: "FAQ 항목은 표준 질문, 유사 질문, 반례 및 여러 답변으로 구성됩니다. 지식베이스 세부 정보에서 일괄 가져오기 및 편집할 수 있습니다.",
       tagDesc: "FAQ 항목에 분류 선택",
+      tagPlaceholder: "분류를 선택하세요",
       modes: {
         questionOnly: "표준 질문/유사 질문만",
         questionAnswer: "표준 질문 + 답변",
diff --git a/frontend/src/i18n/locales/ru-RU.ts b/frontend/src/i18n/locales/ru-RU.ts
index 3a8ad7ad..a78b42bc 100755
--- a/frontend/src/i18n/locales/ru-RU.ts
+++ b/frontend/src/i18n/locales/ru-RU.ts
@@ -1056,6 +1056,7 @@ export default {
       questionIndexModeDescription: 'Объединенная: стандартные и похожие вопросы индексируются вместе. Раздельная: каждый вопрос индексируется независимо для более точного поиска, но требует больше места.',
       entryGuide: 'Каждый FAQ включает основной вопрос, похожие вопросы, негативные примеры и несколько ответов. Управляйте ими в деталях FAQ-базы.',
       tagDesc: 'Выберите категорию для записей FAQ',
+      tagPlaceholder: 'Пожалуйста, выберите категорию',
       modes: {
         questionOnly: 'Только вопросы',
         questionAnswer: 'Вопрос + ответ',
diff --git a/frontend/src/i18n/locales/zh-CN.ts b/frontend/src/i18n/locales/zh-CN.ts
index 7bd9da27..516fce3f 100755
--- a/frontend/src/i18n/locales/zh-CN.ts
+++ b/frontend/src/i18n/locales/zh-CN.ts
@@ -1463,6 +1463,7 @@ export default {
       questionIndexModeDescription: "合并索引：标准问和相似问合并索引；分别索引：标准问和每个相似问独立索引，检索更精确但需要更多存储",
       entryGuide: "FAQ 条目由标准问、相似问、反例和多个答案组成，可在知识库详情中批量导入、编辑。",
       tagDesc: "为 FAQ 条目选择分类",
+      tagPlaceholder: "请选择分类",
       modes: {
         questionOnly: "仅标准问/相似问",
         questionAnswer: "标准问 + 答案",
diff --git a/frontend/src/views/knowledge/KnowledgeBase.vue b/frontend/src/views/knowledge/KnowledgeBase.vue
index 4adce1bd..7ceb815e 100644
--- a/frontend/src/views/knowledge/KnowledgeBase.vue
+++ b/frontend/src/views/knowledge/KnowledgeBase.vue
@@ -46,7 +46,7 @@ let knowledgeScroll = ref()
 let page = 1;
 let pageSize = 35;
 
-const selectedTagId = ref<string>("__untagged__");
+const selectedTagId = ref<string>('');
 const tagList = ref<any[]>([]);
 const tagLoading = ref(false);
 const tagSearchQuery = ref('');
@@ -59,7 +59,6 @@ let tagSearchDebounce: ReturnType<typeof setTimeout> | null = null;
 let docSearchDebounce: ReturnType<typeof setTimeout> | null = null;
 const docSearchKeyword = ref('');
 const selectedFileType = ref('');
-const UNTAGGED_TAG_ID = '__untagged__';
 const fileTypeOptions = computed(() => [
   { content: t('knowledgeBase.allFileTypes') || '全部类型', value: '' },
   { content: 'PDF', value: 'pdf' },
@@ -71,18 +70,12 @@ const fileTypeOptions = computed(() => [
   { content: t('knowledgeBase.typeManual') || '手动创建', value: 'manual' },
 ]);
 type TagInputInstance = ComponentPublicInstance<{ focus: () => void; select: () => void }>;
-const tagDropdownOptions = computed(() => {
-  const options = [
-    { content: t('knowledgeBase.untagged') || '未分类', value: UNTAGGED_TAG_ID },
-    ...tagList.value
-      .filter((tag: any) => tag.id !== UNTAGGED_TAG_ID)
-      .map((tag: any) => ({
-        content: tag.name,
-        value: tag.id,
-      })),
-  ];
-  return options;
-});
+const tagDropdownOptions = computed(() =>
+  tagList.value.map((tag: any) => ({
+    content: tag.name,
+    value: tag.id,
+  })),
+);
 const tagMap = computed<Record<string, any>>(() => {
   const map: Record<string, any> = {};
   tagList.value.forEach((tag) => {
@@ -124,10 +117,9 @@ const getPageSize = () => {
 getPageSize()
 // 直接调用 API 获取知识库文件列表
 const getTagName = (tagId?: string | number) => {
-  if (!tagId && tagId !== 0) return t('knowledgeBase.untagged') || '未分类';
-  if (tagId === UNTAGGED_TAG_ID) return t('knowledgeBase.untagged') || '未分类';
+  if (!tagId && tagId !== 0) return '';
   const key = String(tagId);
-  return tagMap.value[key]?.name || (t('knowledgeBase.untagged') || '未分类');
+  return tagMap.value[key]?.name || '';
 };
 
 const formatDocTime = (time?: string) => {
@@ -225,22 +217,6 @@ const handleTagFilterChange = (value: string) => {
 };
 
 const handleTagRowClick = (tagId: string) => {
-  const normalizedId = String(tagId);
-  if (editingTagId.value && editingTagId.value !== normalizedId) {
-    editingTagId.value = null;
-    editingTagName.value = '';
-  }
-  if (creatingTag.value) {
-    creatingTag.value = false;
-    newTagName.value = '';
-  }
-  if (selectedTagId.value === normalizedId) {
-    return;
-  }
-  handleTagFilterChange(normalizedId);
-};
-
-const handleUntaggedClick = () => {
   if (creatingTag.value) {
     creatingTag.value = false;
     newTagName.value = '';
@@ -249,8 +225,8 @@ const handleUntaggedClick = () => {
     editingTagId.value = null;
     editingTagName.value = '';
   }
-  if (selectedTagId.value === UNTAGGED_TAG_ID) return;
-  handleTagFilterChange(UNTAGGED_TAG_ID);
+  if (selectedTagId.value === tagId) return;
+  handleTagFilterChange(tagId);
 };
 
 const startCreateTag = () => {
@@ -360,7 +336,9 @@ const confirmDeleteTag = (tag: any) => {
     .then(() => {
       MessagePlugin.success(t('knowledgeBase.tagDeleteSuccess'));
       if (selectedTagId.value === tag.id) {
-        handleTagFilterChange(UNTAGGED_TAG_ID);
+        // Reset to show all entries when current tag is deleted
+        selectedTagId.value = '';
+        handleTagFilterChange('');
       }
       loadTags(kbId.value);
       loadKnowledgeFiles(kbId.value);
@@ -372,8 +350,8 @@ const confirmDeleteTag = (tag: any) => {
 
 const handleKnowledgeTagChange = async (knowledgeId: string, tagValue: string) => {
   try {
-    // When selecting "untagged", pass null to clear the tag
-    const tagIdToUpdate = tagValue === UNTAGGED_TAG_ID ? null : (tagValue || null);
+    // Pass the tag value directly (empty string means no tag)
+    const tagIdToUpdate = tagValue || null;
     await updateKnowledgeTagBatch({ updates: { [knowledgeId]: tagIdToUpdate } });
     MessagePlugin.success(t('knowledgeBase.tagUpdateSuccess') || '分类已更新');
     loadKnowledgeFiles(kbId.value);
@@ -392,7 +370,7 @@ const loadKnowledgeBaseInfo = async (targetKbId: string) => {
   try {
     const res: any = await getKnowledgeBaseById(targetKbId);
     kbInfo.value = res?.data || null;
-    selectedTagId.value = UNTAGGED_TAG_ID;
+    selectedTagId.value = '';
     if (!isFAQ.value) {
       loadKnowledgeFiles(targetKbId);
     } else {
@@ -1042,16 +1020,12 @@ async function createNewSession(value: string): Promise<void> {
                   v-for="tag in filteredTags"
                   :key="tag.id"
                   class="tag-list-item"
-                  :class="{ active: selectedTagId === tag.id, editing: editingTagId === tag.id && tag.id !== UNTAGGED_TAG_ID }"
-                  @click="tag.id === UNTAGGED_TAG_ID ? handleUntaggedClick() : handleTagRowClick(tag.id)"
+                  :class="{ active: selectedTagId === tag.id, editing: editingTagId === tag.id }"
+                  @click="handleTagRowClick(tag.id)"
                 >
                   <div class="tag-list-left">
                     <t-icon name="folder" size="18px" />
-                    <!-- Untagged pseudo-tag: show translated name, no editing -->
-                    <template v-if="tag.id === UNTAGGED_TAG_ID">
-                      <span class="tag-name">{{ $t('knowledgeBase.untagged') || '未分类' }}</span>
-                    </template>
-                    <template v-else-if="editingTagId === tag.id">
+                    <template v-if="editingTagId === tag.id">
                       <div class="tag-edit-input" @click.stop>
                         <t-input
                           :ref="setEditingTagInputRefByTag(tag.id)"
@@ -1069,11 +1043,7 @@ async function createNewSession(value: string): Promise<void> {
                   </div>
                   <div class="tag-list-right">
                     <span class="tag-count">{{ tag.knowledge_count || 0 }}</span>
-                    <!-- Untagged pseudo-tag: no edit/delete actions -->
-                    <template v-if="tag.id === UNTAGGED_TAG_ID">
-                      <!-- Empty placeholder for alignment -->
-                    </template>
-                    <template v-else-if="editingTagId === tag.id">
+                    <template v-if="editingTagId === tag.id">
                       <div class="tag-inline-actions" @click.stop>
                         <t-button
                           variant="text"
diff --git a/frontend/src/views/knowledge/components/FAQEntryManager.vue b/frontend/src/views/knowledge/components/FAQEntryManager.vue
index 20aae325..b2ae7175 100644
--- a/frontend/src/views/knowledge/components/FAQEntryManager.vue
+++ b/frontend/src/views/knowledge/components/FAQEntryManager.vue
@@ -183,16 +183,12 @@
                   v-for="tag in filteredTags"
                   :key="tag.id"
                   class="faq-tag-item"
-                  :class="{ active: selectedTagId === tag.id, editing: editingTagId === tag.id && tag.id !== UNTAGGED_FILTER }"
-                  @click="tag.id === UNTAGGED_FILTER ? handleUntaggedClick() : handleTagRowClick(tag.id)"
+                  :class="{ active: selectedTagId === tag.id, editing: editingTagId === tag.id }"
+                  @click="handleTagRowClick(tag.id)"
                 >
                   <div class="faq-tag-left">
                     <t-icon name="folder" size="18px" />
-                    <!-- Untagged pseudo-tag: show translated name, no editing -->
-                    <template v-if="tag.id === UNTAGGED_FILTER">
-                      <span class="tag-name">{{ $t('knowledgeBase.untagged') }}</span>
-                    </template>
-                    <template v-else-if="editingTagId === tag.id">
+                    <template v-if="editingTagId === tag.id">
                       <div class="tag-edit-input" @click.stop>
                         <t-input
                           :ref="setEditingTagInputRefByTag(tag.id)"
@@ -210,11 +206,7 @@
                   </div>
                   <div class="faq-tag-right">
                     <span class="faq-tag-count">{{ tag.chunk_count || 0 }}</span>
-                    <!-- Untagged pseudo-tag: no edit/delete actions, just a placeholder -->
-                    <template v-if="tag.id === UNTAGGED_FILTER">
-                      <div class="tag-more-placeholder"></div>
-                    </template>
-                    <template v-else-if="editingTagId === tag.id">
+                    <template v-if="editingTagId === tag.id">
                       <div class="tag-inline-actions" @click.stop>
                         <t-button
                           variant="text"
@@ -1185,9 +1177,8 @@ type TagInputInstance = ComponentPublicInstance<{ focus: () => void; select: ()
 const tagList = ref<any[]>([])
 const tagLoading = ref(false)
 const tagListRef = ref<HTMLElement | null>(null)
-// Special value to represent "untagged" filter - must match backend constant
-const UNTAGGED_FILTER = '__untagged__'
-const selectedTagId = ref<string>(UNTAGGED_FILTER)
+// Selected tag ID for filtering (empty string means show all)
+const selectedTagId = ref<string>('')
 const overallFAQTotal = ref(0)
 const tagSearchQuery = ref('')
 const TAG_PAGE_SIZE = 20
@@ -1221,16 +1212,14 @@ const tagMap = computed<Record<string, any>>(() => {
   })
   return map
 })
-// Filter out the __untagged__ pseudo-tag for tag select options (when assigning tags)
-const regularTags = computed(() => tagList.value.filter((tag) => tag.id !== UNTAGGED_FILTER))
-const tagDropdownOptions = computed(() => [
-  { content: t('knowledgeBase.untagged') || '未分类', value: '' },
-  ...regularTags.value.map((tag: any) => ({ content: tag.name, value: tag.id })),
-])
-const tagSelectOptions = computed(() => [
-  { label: t('knowledgeBase.untagged') || '未分类', value: '' },
-  ...regularTags.value.map((tag: any) => ({ label: tag.name, value: tag.id })),
-])
+// All tags are now regular tags (no pseudo-tag)
+const regularTags = computed(() => tagList.value)
+const tagDropdownOptions = computed(() =>
+  regularTags.value.map((tag: any) => ({ content: tag.name, value: tag.id })),
+)
+const tagSelectOptions = computed(() =>
+  regularTags.value.map((tag: any) => ({ label: tag.name, value: tag.id })),
+)
 const sidebarCategoryCount = computed(() => tagList.value.length)
 const filteredTags = computed(() => {
   const query = tagSearchQuery.value.trim().toLowerCase()
@@ -1418,17 +1407,6 @@ const handleTagRowClick = (tagId: string) => {
   handleTagFilterChange(normalizedId)
 }
 
-const handleUntaggedClick = () => {
-  if (creatingTag.value) {
-    cancelCreateTag()
-  }
-  if (editingTagId.value) {
-    cancelEditTag()
-  }
-  if (selectedTagId.value === UNTAGGED_FILTER) return
-  handleTagFilterChange(UNTAGGED_FILTER)
-}
-
 const startCreateTag = () => {
   if (!props.kbId) {
     MessagePlugin.warning(t('knowledgeEditor.messages.missingId'))
@@ -1536,7 +1514,9 @@ const confirmDeleteTag = (tag: any) => {
         await deleteKnowledgeBaseTag(props.kbId, tag.id, { force: true })
         MessagePlugin.success(t('knowledgeBase.tagDeleteSuccess'))
         if (selectedTagId.value === tag.id) {
-          handleTagFilterChange(UNTAGGED_FILTER)
+          // Reset to show all entries when current tag is deleted
+          selectedTagId.value = ''
+          handleTagFilterChange('')
         }
         await loadTags()
         await loadEntries()
@@ -2253,7 +2233,7 @@ const startPolling = (taskId: string) => {
           if (status === 'success') {
             MessagePlugin.success(t('knowledgeEditor.faqImport.importSuccess'))
             // 清除筛选条件，确保用户能看到所有新导入的数据
-            selectedTagId.value = UNTAGGED_FILTER
+            selectedTagId.value = ''
             entrySearchKeyword.value = ''
             overallFAQTotal.value = 0  // Reset to trigger re-fetch
             await loadEntries()
@@ -2610,7 +2590,7 @@ watch(
   async (newKbId) => {
     currentPage = 1
     hasMore.value = true
-    selectedTagId.value = UNTAGGED_FILTER
+    selectedTagId.value = ''
     overallFAQTotal.value = 0  // Reset to trigger re-fetch
     cancelCreateTag()
     cancelEditTag()
diff --git a/internal/application/repository/chunk.go b/internal/application/repository/chunk.go
index 919aa8be..a1b4be5b 100644
--- a/internal/application/repository/chunk.go
+++ b/internal/application/repository/chunk.go
@@ -91,10 +91,7 @@ func (r *chunkRepository) ListPagedChunksByKnowledgeID(
 	baseFilter := func(db *gorm.DB) *gorm.DB {
 		db = db.Where("tenant_id = ? AND knowledge_id = ? AND chunk_type IN (?) AND status in (?)",
 			tenantID, knowledgeID, chunkType, []int{int(types.ChunkStatusIndexed), int(types.ChunkStatusDefault)})
-		if tagID == types.UntaggedTagID {
-			// Special value to filter entries without a tag
-			db = db.Where("tag_id = ''")
-		} else if tagID != "" {
+		if tagID != "" {
 			db = db.Where("tag_id = ?", tagID)
 		}
 		if keyword != "" {
@@ -640,9 +637,7 @@ func (r *chunkRepository) UpdateChunkFieldsByTagID(
 			Select("id").
 			Where("tenant_id = ? AND knowledge_base_id = ? AND chunk_type = ?",
 				tenantID, kbID, types.ChunkTypeFAQ)
-		if tagID == "" || tagID == types.UntaggedTagID {
-			query = query.Where("(tag_id = '' OR tag_id IS NULL)")
-		} else {
+		if tagID != "" {
 			query = query.Where("tag_id = ?", tagID)
 		}
 
@@ -669,22 +664,16 @@ func (r *chunkRepository) UpdateChunkFieldsByTagID(
 		updates["is_enabled"] = *isEnabled
 	}
 
-	// Handle newTagID update (__untagged__ is stored as empty string)
+	// Handle newTagID update
 	if newTagID != nil {
-		if *newTagID == types.UntaggedTagID || *newTagID == "" {
-			updates["tag_id"] = ""
-		} else {
-			updates["tag_id"] = *newTagID
-		}
+		updates["tag_id"] = *newTagID
 	}
 
 	query := r.db.WithContext(ctx).Model(&types.Chunk{}).
 		Where("tenant_id = ? AND knowledge_base_id = ? AND chunk_type = ?",
 			tenantID, kbID, types.ChunkTypeFAQ)
 
-	if tagID == "" || tagID == types.UntaggedTagID {
-		query = query.Where("(tag_id = '' OR tag_id IS NULL)")
-	} else {
+	if tagID != "" {
 		query = query.Where("tag_id = ?", tagID)
 	}
 
diff --git a/internal/application/repository/knowledge.go b/internal/application/repository/knowledge.go
index 3d60c077..209dac65 100644
--- a/internal/application/repository/knowledge.go
+++ b/internal/application/repository/knowledge.go
@@ -72,12 +72,7 @@ func (r *knowledgeRepository) ListPagedKnowledgeByKnowledgeBaseID(
 	query := r.db.WithContext(ctx).Model(&types.Knowledge{}).
 		Where("tenant_id = ? AND knowledge_base_id = ?", tenantID, kbID)
 	if tagID != "" {
-		if tagID == types.UntaggedTagID {
-			// Special value to filter entries without a tag
-			query = query.Where("tag_id = '' OR tag_id IS NULL")
-		} else {
-			query = query.Where("tag_id = ?", tagID)
-		}
+		query = query.Where("tag_id = ?", tagID)
 	}
 	if keyword != "" {
 		query = query.Where("file_name LIKE ?", "%"+keyword+"%")
@@ -101,12 +96,7 @@ func (r *knowledgeRepository) ListPagedKnowledgeByKnowledgeBaseID(
 	dataQuery := r.db.WithContext(ctx).
 		Where("tenant_id = ? AND knowledge_base_id = ?", tenantID, kbID)
 	if tagID != "" {
-		if tagID == types.UntaggedTagID {
-			// Special value to filter entries without a tag
-			dataQuery = dataQuery.Where("tag_id = '' OR tag_id IS NULL")
-		} else {
-			dataQuery = dataQuery.Where("tag_id = ?", tagID)
-		}
+		dataQuery = dataQuery.Where("tag_id = ?", tagID)
 	}
 	if keyword != "" {
 		dataQuery = dataQuery.Where("file_name LIKE ?", "%"+keyword+"%")
diff --git a/internal/application/repository/tag.go b/internal/application/repository/tag.go
index 10e651f3..07de1373 100644
--- a/internal/application/repository/tag.go
+++ b/internal/application/repository/tag.go
@@ -136,27 +136,6 @@ func (r *knowledgeTagRepository) CountReferences(
 	return
 }
 
-// CountUntaggedReferences returns the number of knowledges and chunks without a tag
-func (r *knowledgeTagRepository) CountUntaggedReferences(
-	ctx context.Context,
-	tenantID uint64,
-	kbID string,
-) (knowledgeCount int64, chunkCount int64, err error) {
-	if err = r.db.WithContext(ctx).
-		Model(&types.Knowledge{}).
-		Where("tenant_id = ? AND knowledge_base_id = ? AND (tag_id = '' OR tag_id IS NULL)", tenantID, kbID).
-		Count(&knowledgeCount).Error; err != nil {
-		return
-	}
-	if err = r.db.WithContext(ctx).
-		Model(&types.Chunk{}).
-		Where("tenant_id = ? AND knowledge_base_id = ? AND (tag_id = '' OR tag_id IS NULL)", tenantID, kbID).
-		Count(&chunkCount).Error; err != nil {
-		return
-	}
-	return
-}
-
 // DeleteUnusedTags deletes tags that are not referenced by any knowledge or chunk.
 // Returns the number of deleted tags.
 func (r *knowledgeTagRepository) DeleteUnusedTags(ctx context.Context, tenantID uint64, kbID string) (int64, error) {
diff --git a/internal/application/service/knowledge.go b/internal/application/service/knowledge.go
index 1c9f286d..7a01a00c 100644
--- a/internal/application/service/knowledge.go
+++ b/internal/application/service/knowledge.go
@@ -4590,6 +4590,7 @@ func (s *knowledgeService) checkFAQQuestionDuplicate(
 }
 
 // resolveTagID resolves tag ID from payload, prioritizing tag_id over tag_name
+// If no tag is specified, creates or finds the "未分类" tag
 func (s *knowledgeService) resolveTagID(ctx context.Context, kbID string, payload *types.FAQEntryPayload) (string, error) {
 	// 如果提供了 tag_id，优先使用 tag_id
 	if payload.TagID != "" {
@@ -4597,7 +4598,7 @@ func (s *knowledgeService) resolveTagID(ctx context.Context, kbID string, payloa
 	}
 
 	// 如果提供了 tag_name，查找或创建标签
-	if payload.TagName != "" && payload.TagName != "未分类" {
+	if payload.TagName != "" {
 		tag, err := s.tagService.FindOrCreateTagByName(ctx, kbID, payload.TagName)
 		if err != nil {
 			return "", fmt.Errorf("failed to resolve tag by name '%s': %w", payload.TagName, err)
@@ -4605,8 +4606,12 @@ func (s *knowledgeService) resolveTagID(ctx context.Context, kbID string, payloa
 		return tag.ID, nil
 	}
 
-	// 都没有提供，返回空字符串
-	return "", nil
+	// 都没有提供，使用"未分类"标签
+	tag, err := s.tagService.FindOrCreateTagByName(ctx, kbID, types.UntaggedTagName)
+	if err != nil {
+		return "", fmt.Errorf("failed to get or create default untagged tag: %w", err)
+	}
+	return tag.ID, nil
 }
 
 func sanitizeFAQEntryPayload(payload *types.FAQEntryPayload) (*types.FAQChunkMetadata, error) {
diff --git a/internal/application/service/tag.go b/internal/application/service/tag.go
index a6f51251..5cf60543 100644
--- a/internal/application/service/tag.go
+++ b/internal/application/service/tag.go
@@ -72,28 +72,7 @@ func (s *knowledgeTagService) ListTags(
 		return nil, err
 	}
 
-	results := make([]*types.KnowledgeTagWithStats, 0, len(tags)+1)
-
-	// Add untagged pseudo-tag at the beginning (only on first page and when no keyword filter)
-	if page.Page <= 1 && keyword == "" {
-		untaggedKCount, untaggedCCount, err := s.repo.CountUntaggedReferences(ctx, tenantID, kbID)
-		if err != nil {
-			logger.ErrorWithFields(ctx, err, map[string]interface{}{
-				"kb_id": kbID,
-			})
-			return nil, err
-		}
-		results = append(results, &types.KnowledgeTagWithStats{
-			KnowledgeTag: types.KnowledgeTag{
-				ID:              types.UntaggedTagID,
-				TenantID:        tenantID,
-				KnowledgeBaseID: kbID,
-				Name:            "未分类",
-			},
-			KnowledgeCount: untaggedKCount,
-			ChunkCount:     untaggedCCount,
-		})
-	}
+	results := make([]*types.KnowledgeTagWithStats, 0, len(tags))
 
 	for _, tag := range tags {
 		if tag == nil {
@@ -114,11 +93,6 @@ func (s *knowledgeTagService) ListTags(
 		})
 	}
 
-	// Adjust total to include the untagged pseudo-tag
-	if keyword == "" {
-		total++
-	}
-
 	return types.NewPageResult(total, page, results), nil
 }
 
diff --git a/internal/types/faq.go b/internal/types/faq.go
index fd942474..484ff682 100644
--- a/internal/types/faq.go
+++ b/internal/types/faq.go
@@ -230,8 +230,8 @@ type FAQSearchRequest struct {
 	SecondPriorityTagIDs []string `json:"second_priority_tag_ids"` // 第二优先级标签ID列表，限定命中范围，优先级低于第一优先级
 }
 
-// UntaggedTagID is the special tag ID representing uncategorized entries
-const UntaggedTagID = "__untagged__"
+// UntaggedTagName is the default tag name for entries without a tag
+const UntaggedTagName = "未分类"
 
 // FAQEntryFieldsUpdate 单个FAQ条目的字段更新
 type FAQEntryFieldsUpdate struct {
@@ -248,7 +248,7 @@ type FAQEntryFieldsUpdate struct {
 type FAQEntryFieldsBatchUpdate struct {
 	// ByID 按条目ID更新，key为条目ID
 	ByID map[string]FAQEntryFieldsUpdate `json:"by_id,omitempty"`
-	// ByTag 按Tag批量更新，key为TagID（__untagged__表示未分类）
+	// ByTag 按Tag批量更新，key为TagID
 	ByTag map[string]FAQEntryFieldsUpdate `json:"by_tag,omitempty"`
 	// ExcludeIDs 在ByTag操作中需要排除的ID列表
 	ExcludeIDs []string `json:"exclude_ids,omitempty"`
diff --git a/internal/types/interfaces/tag.go b/internal/types/interfaces/tag.go
index 40aa37ad..938ddda3 100644
--- a/internal/types/interfaces/tag.go
+++ b/internal/types/interfaces/tag.go
@@ -48,12 +48,6 @@ type KnowledgeTagRepository interface {
 		kbID string,
 		tagID string,
 	) (knowledgeCount int64, chunkCount int64, err error)
-	// CountUntaggedReferences returns number of knowledges and chunks without a tag.
-	CountUntaggedReferences(
-		ctx context.Context,
-		tenantID uint64,
-		kbID string,
-	) (knowledgeCount int64, chunkCount int64, err error)
 	// DeleteUnusedTags deletes tags that are not referenced by any knowledge or chunk.
 	DeleteUnusedTags(ctx context.Context, tenantID uint64, kbID string) (int64, error)
 }
diff --git a/migrations/versioned/000008_migrate_untagged_faq.down.sql b/migrations/versioned/000008_migrate_untagged_faq.down.sql
new file mode 100644
index 00000000..da049ed9
--- /dev/null
+++ b/migrations/versioned/000008_migrate_untagged_faq.down.sql
@@ -0,0 +1,50 @@
+-- Rollback: This migration cannot be fully rolled back as we don't know which entries
+-- were originally untagged. We can only clear the tag_id for entries that reference
+-- a "未分类" tag, but this may affect entries that were intentionally tagged.
+
+-- WARNING: This rollback is destructive and should only be used if absolutely necessary.
+-- It will set tag_id to empty string for all FAQ entries that reference "未分类" tags.
+
+DO $$
+DECLARE
+    kb_record RECORD;
+    untagged_tag_id VARCHAR(36);
+    updated_chunks INT;
+BEGIN
+    RAISE NOTICE '[Migration 000008 Rollback] WARNING: This rollback will clear tag_id for all FAQ entries referencing "未分类" tags';
+    
+    -- Find all "未分类" tags
+    FOR kb_record IN 
+        SELECT id, tenant_id, knowledge_base_id 
+        FROM knowledge_tags
+        WHERE name = '未分类'
+    LOOP
+        untagged_tag_id := kb_record.id;
+        
+        -- Clear tag_id for chunks referencing this tag
+        UPDATE chunks 
+        SET tag_id = '', updated_at = NOW()
+        WHERE tag_id = untagged_tag_id
+        AND chunk_type = 'faq';
+        
+        GET DIAGNOSTICS updated_chunks = ROW_COUNT;
+        RAISE NOTICE '[Migration 000008 Rollback] Cleared tag_id for % chunks referencing tag %', 
+            updated_chunks, untagged_tag_id;
+
+        -- Clear tag_id in embeddings if column exists
+        IF EXISTS (
+            SELECT 1 FROM information_schema.columns 
+            WHERE table_name = 'embeddings' AND column_name = 'tag_id'
+        ) THEN
+            UPDATE embeddings 
+            SET tag_id = ''
+            WHERE tag_id = untagged_tag_id;
+        END IF;
+
+        -- Delete the "未分类" tag
+        DELETE FROM knowledge_tags WHERE id = untagged_tag_id;
+        RAISE NOTICE '[Migration 000008 Rollback] Deleted "未分类" tag: %', untagged_tag_id;
+    END LOOP;
+
+    RAISE NOTICE '[Migration 000008 Rollback] Completed rollback';
+END $$;
diff --git a/migrations/versioned/000008_migrate_untagged_faq.up.sql b/migrations/versioned/000008_migrate_untagged_faq.up.sql
new file mode 100644
index 00000000..5e5f3e26
--- /dev/null
+++ b/migrations/versioned/000008_migrate_untagged_faq.up.sql
@@ -0,0 +1,73 @@
+-- Migration: Create "未分类" tag for each knowledge base that has untagged FAQ entries
+-- and update those entries to reference the new tag
+
+DO $$
+DECLARE
+    kb_record RECORD;
+    new_tag_id VARCHAR(36);
+    updated_chunks INT;
+    updated_embeddings INT;
+BEGIN
+    -- Find all knowledge bases that have FAQ chunks with empty or NULL tag_id
+    FOR kb_record IN 
+        SELECT DISTINCT c.tenant_id, c.knowledge_base_id 
+        FROM chunks c
+        WHERE c.chunk_type = 'faq' 
+        AND (c.tag_id = '' OR c.tag_id IS NULL)
+    LOOP
+        -- Check if "未分类" tag already exists for this knowledge base
+        SELECT id INTO new_tag_id
+        FROM knowledge_tags
+        WHERE tenant_id = kb_record.tenant_id 
+        AND knowledge_base_id = kb_record.knowledge_base_id 
+        AND name = '未分类'
+        LIMIT 1;
+
+        -- If not exists, create the tag
+        IF new_tag_id IS NULL THEN
+            new_tag_id := gen_random_uuid()::VARCHAR(36);
+            INSERT INTO knowledge_tags (id, tenant_id, knowledge_base_id, name, color, sort_order, created_at, updated_at)
+            VALUES (new_tag_id, kb_record.tenant_id, kb_record.knowledge_base_id, '未分类', '', 0, NOW(), NOW());
+            RAISE NOTICE '[Migration 000008] Created "未分类" tag (id: %) for tenant_id: %, kb_id: %', 
+                new_tag_id, kb_record.tenant_id, kb_record.knowledge_base_id;
+        ELSE
+            RAISE NOTICE '[Migration 000008] "未分类" tag already exists (id: %) for tenant_id: %, kb_id: %', 
+                new_tag_id, kb_record.tenant_id, kb_record.knowledge_base_id;
+        END IF;
+
+        -- Update chunks with empty tag_id to use the new tag
+        UPDATE chunks 
+        SET tag_id = new_tag_id, updated_at = NOW()
+        WHERE tenant_id = kb_record.tenant_id 
+        AND knowledge_base_id = kb_record.knowledge_base_id 
+        AND chunk_type = 'faq'
+        AND (tag_id = '' OR tag_id IS NULL);
+        
+        GET DIAGNOSTICS updated_chunks = ROW_COUNT;
+        RAISE NOTICE '[Migration 000008] Updated % chunks for tenant_id: %, kb_id: %', 
+            updated_chunks, kb_record.tenant_id, kb_record.knowledge_base_id;
+
+        -- Update embeddings with empty tag_id (if embeddings table exists and has tag_id column)
+        IF EXISTS (
+            SELECT 1 FROM information_schema.columns 
+            WHERE table_name = 'embeddings' AND column_name = 'tag_id'
+        ) THEN
+            UPDATE embeddings 
+            SET tag_id = new_tag_id
+            WHERE knowledge_base_id = kb_record.knowledge_base_id 
+            AND (tag_id = '' OR tag_id IS NULL)
+            AND chunk_id IN (
+                SELECT id FROM chunks 
+                WHERE tenant_id = kb_record.tenant_id 
+                AND knowledge_base_id = kb_record.knowledge_base_id 
+                AND chunk_type = 'faq'
+            );
+            
+            GET DIAGNOSTICS updated_embeddings = ROW_COUNT;
+            RAISE NOTICE '[Migration 000008] Updated % embeddings for kb_id: %', 
+                updated_embeddings, kb_record.knowledge_base_id;
+        END IF;
+    END LOOP;
+
+    RAISE NOTICE '[Migration 000008] Completed migration of untagged FAQ entries';
+END $$;