diff --git a/frontend/src/i18n/locales/en/collectors.ts b/frontend/src/i18n/locales/en/collectors.ts
index 0d9b3ef..cf1d425 100644
--- a/frontend/src/i18n/locales/en/collectors.ts
+++ b/frontend/src/i18n/locales/en/collectors.ts
@@ -121,6 +121,7 @@ const collectors = {
     namespaces: 'Namespaces to Collect',
     allNamespaces: 'All namespaces cluster-wide',
     selectedCount: '{{count}} selected',
+    allCheckedHint: '(tick any namespace below to switch to a fixed set)',
     allCheckbox: 'All namespaces (collect cluster-wide)',
     nsSearch: 'Search namespaces…',
     loading: 'Loading…',
diff --git a/frontend/src/i18n/locales/zh/collectors.ts b/frontend/src/i18n/locales/zh/collectors.ts
index 06cf685..110da48 100644
--- a/frontend/src/i18n/locales/zh/collectors.ts
+++ b/frontend/src/i18n/locales/zh/collectors.ts
@@ -125,6 +125,7 @@ const collectors = {
     namespaces: '采集命名空间',
     allNamespaces: '全集群所有命名空间',
     selectedCount: '已选 {{count}} 个',
+    allCheckedHint: '（勾选下方任一命名空间即可改为只采指定范围）',
     allCheckbox: '所有命名空间（全集群采集）',
     nsSearch: '搜索命名空间…',
     loading: '加载中…',
diff --git a/frontend/src/pages/collectors/components/CollectorEditDialog.tsx b/frontend/src/pages/collectors/components/CollectorEditDialog.tsx
index 89f7a80..3b2e10b 100644
--- a/frontend/src/pages/collectors/components/CollectorEditDialog.tsx
+++ b/frontend/src/pages/collectors/components/CollectorEditDialog.tsx
@@ -290,7 +290,12 @@ export const CollectorEditDialog = memo(function CollectorEditDialog({ collector
                     <div className="rounded-md border">
                       <label className="flex items-center gap-2 border-b px-3 py-2 text-sm font-medium cursor-pointer hover:bg-muted/50">
                         <Checkbox checked={allSelected} onCheckedChange={() => setAll()} />
-                        {t('edit.allCheckbox')}
+                        <span className="flex-1">{t('edit.allCheckbox')}</span>
+                        {allSelected && (
+                          <span className="text-xs font-normal text-muted-foreground">
+                            {t('edit.allCheckedHint')}
+                          </span>
+                        )}
                       </label>
                       <div className="p-2">
                         <Input
@@ -308,9 +313,13 @@ export const CollectorEditDialog = memo(function CollectorEditDialog({ collector
                           )}
                           {filteredNs.map((ns) => (
                             <label key={ns} className="flex items-center gap-2 rounded px-2 py-1 text-sm hover:bg-muted/50 cursor-pointer">
+                              {/* 这里**不能**用 disabled={allSelected}：
+                                  "全集群"状态下列表为空，一旦禁用所有子项，
+                                  用户就永远无法从"全集群"切到"只采几个"——
+                                  勾任何一个都会把 allSelected 变成 false，
+                                  从而自动退出全集群状态。 */}
                               <input
                                 type="checkbox"
-                                disabled={allSelected}
                                 checked={selectedNs.includes(ns)}
                                 onChange={() => toggleNs(ns)}
                               />