diff --git a/web/app/components/plugins/marketplace/list/collection-list.tsx b/web/app/components/plugins/marketplace/list/collection-list.tsx
index 0af7eb2d7b..5c2a3480bf 100644
--- a/web/app/components/plugins/marketplace/list/collection-list.tsx
+++ b/web/app/components/plugins/marketplace/list/collection-list.tsx
@@ -46,7 +46,7 @@ export function ViewMoreButton({ searchParams, searchTab }: ViewMoreButtonProps)
 
   return (
     <div
-      className="system-xs-medium flex cursor-pointer items-center text-text-accent"
+      className="flex cursor-pointer items-center text-text-accent system-xs-medium"
       onClick={() => onMoreClick(searchParams, searchTab)}
     >
       {t('marketplace.viewMore', { ns: 'plugin' })}
@@ -72,14 +72,23 @@ export function CollectionHeader<TCollection extends BaseCollection>({
     && !!collection.search_params
     && itemsLength > GRID_DISPLAY_LIMIT
 
+  // The API only ships translations for a subset of locales (typically en_US
+  // and zh_Hans). For any other locale (e.g. ja_JP, pt_BR) the keyed lookup
+  // returns undefined and the title/description render as empty divs. Fall
+  // back to the en_US translation, then to whatever value is available, so
+  // the header always shows something meaningful.
+  const lang = getLanguage(locale)
+  const label = collection.label[lang] || collection.label.en_US || Object.values(collection.label)[0] || ''
+  const description = collection.description[lang] || collection.description.en_US || Object.values(collection.description)[0] || ''
+
   return (
     <div className="mb-2 flex items-end justify-between">
       <div>
-        <div className="title-xl-semi-bold text-text-primary">
-          {collection.label[getLanguage(locale)]}
+        <div className="text-text-primary title-xl-semi-bold">
+          {label}
         </div>
-        <div className="system-xs-regular text-text-tertiary">
-          {collection.description[getLanguage(locale)]}
+        <div className="text-text-tertiary system-xs-regular">
+          {description}
         </div>
       </div>
       {showViewMore && viewMore}
diff --git a/web/app/components/plugins/marketplace/search-page/constants.ts b/web/app/components/plugins/marketplace/search-page/constants.ts
index 10da9c572b..238fb084ea 100644
--- a/web/app/components/plugins/marketplace/search-page/constants.ts
+++ b/web/app/components/plugins/marketplace/search-page/constants.ts
@@ -6,10 +6,7 @@ export type LanguageOption = {
 
 export const LANGUAGE_OPTIONS: LanguageOption[] = [
   { value: 'en', label: 'English', nativeLabel: 'English' },
-  { value: 'zh-Hans', label: 'Simplified Chinese', nativeLabel: '简体中文' },
-  { value: 'zh-Hant', label: 'Traditional Chinese', nativeLabel: '繁體中文' },
+  { value: 'zh-Hans', label: 'Simplified Chinese', nativeLabel: '中文' },
   { value: 'ja', label: 'Japanese', nativeLabel: '日本語' },
-  { value: 'es', label: 'Spanish', nativeLabel: 'Español' },
-  { value: 'fr', label: 'French', nativeLabel: 'Français' },
-  { value: 'ko', label: 'Korean', nativeLabel: '한국어' },
+  { value: 'other', label: 'Other', nativeLabel: 'Other' },
 ]
diff --git a/web/app/components/plugins/marketplace/state.ts b/web/app/components/plugins/marketplace/state.ts
index a214e56375..5f3fd95d90 100644
--- a/web/app/components/plugins/marketplace/state.ts
+++ b/web/app/components/plugins/marketplace/state.ts
@@ -6,6 +6,7 @@ import { CATEGORY_ALL } from './constants'
 import { useMarketplaceContainerScroll } from './hooks'
 import { useMarketplaceCollectionsAndPlugins, useMarketplacePlugins, useMarketplaceTemplateCollectionsAndTemplates, useMarketplaceTemplates } from './query'
 import { CREATION_TYPE } from './search-params'
+import { useTemplateCollectionsMapFilteredBySystemLanguage, useTemplatesFilteredBySystemLanguage } from './use-sync-system-language'
 import { getCollectionsParams, getPluginFilterType, mapTemplateDetailToTemplate } from './utils'
 
 const getCategory = (category: string) => {
@@ -112,10 +113,31 @@ export function useTemplatesMarketplaceData(enabled = true) {
   // Scroll pagination
   useMarketplaceContainerScroll(handlePageChange)
 
+  // Raw templates as returned by the API (after pagination/flattening).
+  const rawTemplates = useMemo(
+    () => templatesQuery.data?.pages.flatMap(page => page.templates).map(mapTemplateDetailToTemplate),
+    [templatesQuery.data],
+  )
+
+  // If the "Filter by language" dropdown is empty, post-filter the returned
+  // templates by the user's system language. If the dropdown has any picks,
+  // pass the list through untouched (the server has already filtered).
+  //
+  // The same rule applies to the curated-collections layout, which is what
+  // the page renders in default mode (no search, no category, no manual
+  // filter) — without this, the system-language filter never visibly takes
+  // effect on first entry.
+  const hasManualFilter = filterTemplateLanguages.length > 0
+  const templates = useTemplatesFilteredBySystemLanguage(rawTemplates, hasManualFilter)
+  const templateCollectionTemplatesMap = useTemplateCollectionsMapFilteredBySystemLanguage(
+    templateCollectionsQuery.data?.templateCollectionTemplatesMap,
+    hasManualFilter,
+  )
+
   return {
     templateCollections: templateCollectionsQuery.data?.templateCollections,
-    templateCollectionTemplatesMap: templateCollectionsQuery.data?.templateCollectionTemplatesMap,
-    templates: templatesQuery.data?.pages.flatMap(page => page.templates).map(mapTemplateDetailToTemplate),
+    templateCollectionTemplatesMap,
+    templates,
     templatesTotal: templatesQuery.data?.pages[0]?.total,
     page: templatesQuery.data?.pages.length || 1,
     isLoading: templateCollectionsQuery.isLoading || templatesQuery.isLoading,
diff --git a/web/app/components/plugins/marketplace/use-sync-system-language.ts b/web/app/components/plugins/marketplace/use-sync-system-language.ts
new file mode 100644
index 0000000000..7c16ef2d99
--- /dev/null
+++ b/web/app/components/plugins/marketplace/use-sync-system-language.ts
@@ -0,0 +1,106 @@
+import type { Template } from './types'
+import { useMemo } from 'react'
+import { useLocale } from '@/context/i18n'
+
+export type TemplateLanguageBucket = 'en' | 'zh' | 'ja' | 'other'
+
+/**
+ * Map the user's system locale to one of the four template-language buckets
+ * exposed by LANGUAGE_OPTIONS:
+ *
+ *   - en-* (e.g. en-US)        → 'en'
+ *   - zh-Hans, zh-Hant, zh-*   → 'zh'
+ *   - ja-* (e.g. ja-JP)        → 'ja'
+ *   - anything else            → 'other'
+ */
+export function localeToLanguageBucket(locale: string): TemplateLanguageBucket {
+  const lower = locale.toLowerCase()
+  if (lower.startsWith('en'))
+    return 'en'
+  if (lower.startsWith('zh'))
+    return 'zh'
+  if (lower.startsWith('ja'))
+    return 'ja'
+  return 'other'
+}
+
+/**
+ * Test whether a template's `preferred_languages` belong to a given bucket.
+ *
+ *   - 'en' bucket: at least one entry starts with 'en'
+ *   - 'zh' bucket: at least one entry starts with 'zh'
+ *   - 'ja' bucket: at least one entry starts with 'ja'
+ *   - 'other' bucket: NONE of the entries start with en / zh / ja (this also
+ *     matches templates that have an empty preferred_languages array)
+ */
+export function templateMatchesBucket(
+  template: Pick<Template, 'preferred_languages'>,
+  bucket: TemplateLanguageBucket,
+): boolean {
+  const langs = (template.preferred_languages || []).map(l => l.toLowerCase())
+
+  if (bucket === 'other') {
+    return !langs.some(l =>
+      l.startsWith('en') || l.startsWith('zh') || l.startsWith('ja'),
+    )
+  }
+
+  return langs.some(l => l.startsWith(bucket))
+}
+
+/**
+ * Filter the templates list by the user's system language when they have
+ * NOT manually selected a language in the "Filter by language" dropdown.
+ *
+ *   - When `hasManualFilter` is true, the server has already filtered the
+ *     list, so the input is returned untouched.
+ *   - Otherwise, the list is filtered client-side by the bucket derived
+ *     from the current system locale. Changing the system locale causes
+ *     this hook to re-compute and the visible list refreshes — but the
+ *     templates `search/advanced` API is NOT refired (its queryKey doesn't
+ *     depend on the locale).
+ */
+export function useTemplatesFilteredBySystemLanguage<
+  T extends Pick<Template, 'preferred_languages'>,
+>(
+  templates: T[] | undefined,
+  hasManualFilter: boolean,
+): T[] | undefined {
+  const locale = useLocale()
+  return useMemo(() => {
+    if (!templates)
+      return undefined
+    if (hasManualFilter)
+      return templates
+    const bucket = localeToLanguageBucket(locale)
+    return templates.filter(t => templateMatchesBucket(t, bucket))
+  }, [templates, hasManualFilter, locale])
+}
+
+/**
+ * Same as `useTemplatesFilteredBySystemLanguage`, but for the collection →
+ * templates map used by the curated-collections layout. Each collection's
+ * template list is filtered independently.
+ *
+ * Empty collections (where every template was filtered out) are kept in
+ * the map; the consumer can decide whether to hide them.
+ */
+export function useTemplateCollectionsMapFilteredBySystemLanguage<
+  T extends Pick<Template, 'preferred_languages'>,
+>(
+  map: Record<string, T[]> | undefined,
+  hasManualFilter: boolean,
+): Record<string, T[]> | undefined {
+  const locale = useLocale()
+  return useMemo(() => {
+    if (!map)
+      return undefined
+    if (hasManualFilter)
+      return map
+    const bucket = localeToLanguageBucket(locale)
+    const filtered: Record<string, T[]> = {}
+    for (const key of Object.keys(map))
+      filtered[key] = map[key].filter(t => templateMatchesBucket(t, bucket))
+    return filtered
+  }, [map, hasManualFilter, locale])
+}