diff --git a/frontend/src/features/plugins/PluginSettingsPanel.spec.ts b/frontend/src/features/plugins/PluginSettingsPanel.spec.ts
index c8fa78b..30bcf17 100644
--- a/frontend/src/features/plugins/PluginSettingsPanel.spec.ts
+++ b/frontend/src/features/plugins/PluginSettingsPanel.spec.ts
@@ -9,7 +9,69 @@ vi.mock('@/services/pluginService', () => ({ getPluginSettings: vi.fn(), updateP
 const schema = (value = ''): PluginSettingsSchema => ({ plugin_id: 'demo', schema_version: 1, fields: [{ key: 'name', label: 'Name', type: 'string', description: '', required: false, options: [] }], values: { name: value }, secrets: {} })
 let wrapper: VueWrapper
 beforeEach(() => { vi.resetAllMocks(); vi.mocked(service.getPluginSettings).mockResolvedValue(schema()) })
-afterEach(() => wrapper?.unmount())
+afterEach(() => { wrapper?.unmount(); vi.unstubAllGlobals() })
+
+function secretSchema(configured = false): PluginSettingsSchema {
+  return { ...schema(), fields: [{ key: 'token', label: 'Token', type: 'secret', description: '', required: false, options: [] }], secrets: { token: { configured } } }
+}
+
+it('preserves new secret input during a pending save and allows saving it next', async () => {
+  vi.mocked(service.getPluginSettings).mockResolvedValue(secretSchema())
+  let finish!: (value: Awaited<ReturnType<typeof service.putPluginSecret>>) => void
+  vi.mocked(service.putPluginSecret).mockReturnValueOnce(new Promise(resolve => { finish = resolve }))
+  wrapper = mount(PluginSettingsPanel, { props: { pluginId: 'demo' } })
+  await flushPromises()
+  await wrapper.get('input[type="password"]').setValue('first-fixture-value')
+  await wrapper.get('.secret-row button').trigger('click')
+  await wrapper.get('input[type="password"]').setValue('second-fixture-value')
+  await wrapper.get('.secret-row button').trigger('click')
+  expect(service.putPluginSecret).toHaveBeenCalledTimes(1)
+  finish({ plugin_id: 'demo', key: 'token', configured: true })
+  await flushPromises()
+  expect((wrapper.get('input[type="password"]').element as HTMLInputElement).value).toBe('second-fixture-value')
+  vi.mocked(service.putPluginSecret).mockResolvedValueOnce({ plugin_id: 'demo', key: 'token', configured: true })
+  await wrapper.get('.secret-row button').trigger('click')
+  await flushPromises()
+  expect(service.putPluginSecret).toHaveBeenLastCalledWith('demo', 'token', 'second-fixture-value')
+  expect((wrapper.get('input[type="password"]').element as HTMLInputElement).value).toBe('')
+})
+
+it('retains a secret draft on failure and allows retry', async () => {
+  vi.mocked(service.getPluginSettings).mockResolvedValue(secretSchema())
+  vi.mocked(service.putPluginSecret).mockRejectedValueOnce(new Error('Save failed'))
+  wrapper = mount(PluginSettingsPanel, { props: { pluginId: 'demo' } })
+  await flushPromises()
+  await wrapper.get('input[type="password"]').setValue('retry-fixture-value')
+  await wrapper.get('.secret-row button').trigger('click')
+  await flushPromises()
+  expect((wrapper.get('input[type="password"]').element as HTMLInputElement).value).toBe('retry-fixture-value')
+  expect(wrapper.get('.secret-row button').attributes('disabled')).toBeUndefined()
+  expect(wrapper.text()).toContain('Save failed')
+})
+
+it.each(['save', 'delete'] as const)('ignores old secret %s responses after switching plugins', async action => {
+  vi.mocked(service.getPluginSettings).mockResolvedValue(secretSchema(true))
+  let finish!: () => void
+  vi.mocked(service.putPluginSecret).mockReturnValue(new Promise(resolve => { finish = () => resolve({ plugin_id: 'demo', key: 'token', configured: true }) }))
+  if (action === 'delete') {
+    vi.stubGlobal('confirm', vi.fn(() => true))
+    vi.mocked(service.deletePluginSecret).mockReturnValue(new Promise(resolve => { finish = () => resolve({ plugin_id: 'demo', key: 'token', configured: false }) }))
+  }
+  wrapper = mount(PluginSettingsPanel, { props: { pluginId: 'demo' } })
+  await flushPromises()
+  await wrapper.get('input[type="password"]').setValue('old-fixture-value')
+  await wrapper.get(action === 'save' ? '.secret-row button' : '.secret-row .danger').trigger('click')
+  vi.mocked(service.getPluginSettings).mockResolvedValue(secretSchema(false))
+  await wrapper.setProps({ pluginId: 'other' })
+  await flushPromises()
+  await wrapper.get('input[type="password"]').setValue('new-fixture-value')
+  finish()
+  await flushPromises()
+  expect((wrapper.get('input[type="password"]').element as HTMLInputElement).value).toBe('new-fixture-value')
+  expect(wrapper.find('.secret-status').classes()).toContain('not-configured')
+  expect(wrapper.emitted('saved')).toBeUndefined()
+  vi.restoreAllMocks()
+})
 
 it('retains edits made during a save and submits them on the next save', async () => {
   let resolveSave!: (value: PluginSettingsSchema) => void
diff --git a/frontend/src/features/plugins/PluginSettingsPanel.vue b/frontend/src/features/plugins/PluginSettingsPanel.vue
index b51281f..7f17227 100644
--- a/frontend/src/features/plugins/PluginSettingsPanel.vue
+++ b/frontend/src/features/plugins/PluginSettingsPanel.vue
@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { computed, onMounted, reactive, ref, watch } from 'vue'
+import { computed, onBeforeUnmount, onMounted, reactive, ref, watch } from 'vue'
 import type { PluginSettingsSchema, PluginSettingField } from '@/contracts'
 import {
   getPluginSettings,
@@ -83,33 +83,45 @@ async function save() {
 }
 
 async function saveSecret(key: string) {
-  if (!secrets[key]) return
+  if (!schema.value || !secrets[key] || isSaving.value) return
+  const version = loadVersion
+  const pluginId = props.pluginId
+  const submittedSecret = secrets[key]
   isSaving.value = true
   saveError.value = ''
   try {
-    const result = await putPluginSecret(props.pluginId, key, secrets[key])
+    const result = await putPluginSecret(pluginId, key, submittedSecret)
+    if (version !== loadVersion || pluginId !== props.pluginId) return
     if (schema.value) {
       schema.value.secrets[key] = { configured: result.configured }
     }
-    secrets[key] = ''
+    if (secrets[key] === submittedSecret) secrets[key] = ''
     emit('saved')
   } catch (error) {
-    saveError.value = error instanceof Error ? error.message : '密钥保存失败'
+    if (version === loadVersion && pluginId === props.pluginId) saveError.value = error instanceof Error ? error.message : '密钥保存失败'
   } finally {
-    isSaving.value = false
+    if (version === loadVersion && pluginId === props.pluginId) isSaving.value = false
   }
 }
 
 async function clearSecret(key: string) {
+  if (!schema.value || isSaving.value) return
   if (!confirm(`确认删除 " ${key} " 的配置？`)) return
+  const version = loadVersion
+  const pluginId = props.pluginId
+  isSaving.value = true
+  saveError.value = ''
   try {
-    await deletePluginSecret(props.pluginId, key)
+    await deletePluginSecret(pluginId, key)
+    if (version !== loadVersion || pluginId !== props.pluginId) return
     if (schema.value) {
       schema.value.secrets[key] = { configured: false }
     }
     emit('saved')
   } catch (error) {
-    saveError.value = error instanceof Error ? error.message : '删除失败'
+    if (version === loadVersion && pluginId === props.pluginId) saveError.value = error instanceof Error ? error.message : '删除失败'
+  } finally {
+    if (version === loadVersion && pluginId === props.pluginId) isSaving.value = false
   }
 }
 
@@ -127,6 +139,7 @@ function setFieldValue(key: string, value: unknown, field: PluginSettingField) {
 }
 
 onMounted(load)
+onBeforeUnmount(() => { loadVersion++ })
 watch(() => props.pluginId, load)
 </script>
 
@@ -220,10 +233,10 @@ watch(() => props.pluginId, load)
                   placeholder="重新输入以更新"
                   class="input"
                 />
-                <button class="button-secondary" :disabled="!secrets[field.key]" @click="saveSecret(field.key)">
+                <button class="button-secondary" :disabled="!secrets[field.key] || isSaving" @click="saveSecret(field.key)">
                   更新
                 </button>
-                <button class="link-btn danger" @click="clearSecret(field.key)">清除</button>
+                <button class="link-btn danger" :disabled="isSaving" @click="clearSecret(field.key)">清除</button>
               </template>
               <template v-else>
                 <input
@@ -234,7 +247,7 @@ watch(() => props.pluginId, load)
                 />
                 <button
                   class="button-primary"
-                  :disabled="!secrets[field.key]"
+                  :disabled="!secrets[field.key] || isSaving"
                   @click="saveSecret(field.key)"
                 >保存</button>
               </template>
diff --git a/frontend/src/features/themes/CommunityThemePreview.vue b/frontend/src/features/themes/CommunityThemePreview.vue
new file mode 100644
index 0000000..b1e5ecb
--- /dev/null
+++ b/frontend/src/features/themes/CommunityThemePreview.vue
@@ -0,0 +1,41 @@
+<script setup lang="ts">
+import { computed } from 'vue'
+import { t } from '@/i18n'
+import { getCommunityThemePreviewCss, mockCommunityThemes } from '@/services/themePackageService'
+import tokensCss from '@/styles/tokens.css?raw'
+
+const props = defineProps<{ themeId: string }>()
+const emit = defineEmits<{ (event: 'close'): void }>()
+const theme = computed(() => mockCommunityThemes.find(item => item.theme_id === props.themeId))
+const previewDocument = computed(() => {
+  // Only bundled community CSS enters this script-free, isolated document.
+  // Previewing never installs a theme or changes application styles/storage.
+  const doc = document.implementation.createHTMLDocument(theme.value?.name ?? '')
+  doc.documentElement.dataset.theme = props.themeId
+  const style = doc.createElement('style')
+  style.textContent = `${tokensCss}\n${getCommunityThemePreviewCss(props.themeId)}\nbody { margin:0; padding:24px; background:var(--color-background-primary); color:var(--color-text-primary); font:16px/1.6 system-ui; } article { padding:20px; border:1px solid var(--color-border-default); border-radius:8px; background:var(--color-surface-primary); } p { color:var(--color-text-secondary); } button { padding:8px 16px; border:0; border-radius:6px; background:var(--color-accent-primary); color:white; }`
+  doc.head.append(style)
+  const article = doc.createElement('article')
+  const heading = doc.createElement('h1'); heading.textContent = theme.value?.name ?? props.themeId
+  const text = doc.createElement('p'); text.textContent = t('知识的价值不只在于保存，更在于被重新发现和使用。', 'Knowledge gains value when it can be rediscovered and used.')
+  const button = doc.createElement('button'); button.textContent = t('示例按钮', 'Example button')
+  article.append(heading, text, button); doc.body.append(article)
+  return '<!doctype html>' + doc.documentElement.outerHTML
+})
+</script>
+
+<template>
+  <div class="modal-backdrop" @click.self="emit('close')" @keydown.esc="emit('close')">
+    <section class="modal theme-preview-dialog" role="dialog" aria-modal="true" :aria-label="t('社区主题预览', 'Community theme preview')">
+      <div class="preview-heading"><h2>{{ theme?.name }}</h2><button class="button-secondary" autofocus @click="emit('close')">{{ t('关闭预览', 'Close preview') }}</button></div>
+      <iframe :title="`${t('主题预览', 'Theme preview')}: ${theme?.name ?? themeId}`" sandbox="" :srcdoc="previewDocument" />
+      <p class="subtle">{{ t('仅预览，不会安装或更改当前主题。', 'Preview only. Your installed themes and current appearance remain unchanged.') }}</p>
+    </section>
+  </div>
+</template>
+
+<style scoped>
+.theme-preview-dialog { width: min(720px, calc(100vw - 32px)); }
+.preview-heading { display: flex; align-items: center; justify-content: space-between; gap: 16px; }
+iframe { display: block; width: 100%; height: min(420px, 60vh); margin: 16px 0; border: 1px solid var(--color-border-default); border-radius: 8px; }
+</style>
diff --git a/frontend/src/features/themes/ThemesView.spec.ts b/frontend/src/features/themes/ThemesView.spec.ts
new file mode 100644
index 0000000..e913295
--- /dev/null
+++ b/frontend/src/features/themes/ThemesView.spec.ts
@@ -0,0 +1,37 @@
+// @vitest-environment happy-dom
+import { afterEach, beforeEach, expect, it, vi } from 'vitest'
+import { flushPromises, mount, type VueWrapper } from '@vue/test-utils'
+import { createPinia, setActivePinia } from 'pinia'
+import ThemesView from './ThemesView.vue'
+import { useThemeStore } from '@/stores/theme'
+import { mockCommunityThemes, getCommunityThemePreviewCss } from '@/services/themePackageService'
+
+let wrapper: VueWrapper
+beforeEach(() => { localStorage.clear(); setActivePinia(createPinia()) })
+afterEach(() => { wrapper?.unmount(); vi.useRealTimers() })
+
+it.each(mockCommunityThemes)('previews uninstalled $theme_id using its actual CSS without changing the active theme', async theme => {
+  const store = useThemeStore()
+  store.applyTheme('light')
+  wrapper = mount(ThemesView, { global: { stubs: { MarkdownContent: true } } })
+  await flushPromises()
+  await wrapper.findAll('.tab-btn')[1]!.trigger('click')
+  const card = wrapper.findAll('article.theme-card').find(item => item.text().includes(theme.name))!
+  await card.findAll('button').find(button => button.text() === '预览')!.trigger('click')
+  expect(wrapper.get('[role="dialog"]').text()).toContain(theme.name)
+  const frame = wrapper.get('iframe')
+  expect(frame.attributes('sandbox')).toBe('')
+  const preview = new DOMParser().parseFromString(frame.attributes('srcdoc')!, 'text/html')
+  expect(preview.documentElement.dataset.theme).toBe(theme.theme_id)
+  expect(preview.querySelector('style')!.textContent).toContain(getCommunityThemePreviewCss(theme.theme_id))
+  expect(store.currentThemeId).toBe('light')
+  expect(localStorage.getItem('theme')).toBe('light')
+  expect(store.isThemeInstalled(theme.theme_id)).toBe(false)
+  expect(document.head.querySelectorAll('style[id^="theme-style-"]')).toHaveLength(0)
+  vi.useFakeTimers()
+  await wrapper.get('[role="dialog"] button').trigger('click')
+  store.applyTheme('dark')
+  await vi.advanceTimersByTimeAsync(2000)
+  expect(wrapper.find('iframe').exists()).toBe(false)
+  expect(store.currentThemeId).toBe('dark')
+})
diff --git a/frontend/src/features/themes/ThemesView.vue b/frontend/src/features/themes/ThemesView.vue
index 7e4c9e6..f1b4c72 100644
--- a/frontend/src/features/themes/ThemesView.vue
+++ b/frontend/src/features/themes/ThemesView.vue
@@ -5,12 +5,14 @@ import { useThemeStore } from '@/stores/theme'
 import { mockCommunityThemes } from '@/services/themePackageService'
 import type { ThemePackageInspection } from '@/contracts'
 import { t } from '@/i18n'
+import CommunityThemePreview from './CommunityThemePreview.vue'
 
 const themeStore = useThemeStore()
 
 const activeTab = ref<'installed' | 'community'>('installed')
 const showImportDialog = ref(false)
 const previewThemeId = ref<string | null>(null)
+const communityPreviewId = ref<string | null>(null)
 const actionError = ref('')
 
 const shikiPreview = `\`\`\`typescript
@@ -71,10 +73,7 @@ async function installFromCommunity(themeId: string) {
 }
 
 function previewCommunity(themeId: string) {
-  // 临时切换预览
-  const current = themeStore.currentThemeId
-  themeStore.applyTheme(themeId)
-  setTimeout(() => themeStore.applyTheme(current), 1500)
+  communityPreviewId.value = themeId
 }
 
 onMounted(() => {
@@ -84,6 +83,7 @@ onMounted(() => {
 
 <template>
   <section class="feature-page">
+    <CommunityThemePreview v-if="communityPreviewId" :theme-id="communityPreviewId" @close="communityPreviewId = null" />
     <header class="feature-header">
       <div>
         <h1>{{ t('主题', 'Themes') }}</h1>