@@ -0,0 +1,10 @@
+---
+'@objectstack/service-storage': patch
+---
+
+fix(service-storage): Setup → Storage → Test connection answers in the caller's language
+
+Clause-②: no
+Metadata-protocol: none
+
+The `storage/test` settings action writes its `message` in the language the settings action route hands its handler as `locale` (`Accept-Language`, else `?locale`), the same source the mail test notice reads. It covers the sentences the product writes: the success sentence (which still names the adapter), the refusal when the probe read back is not the one written, and the refusal for S3 settings missing a bucket or a region. An adapter's own error text stays verbatim: alone in English, as before; in another language behind a lead-in saying the connection test failed. Every language on the platform locale table is served (`en`, `zh-CN`, `zh-Hant`, `es-ES`, `ar`, `fr`, `pt-BR`, `ru`, `de`, `ja-JP`, `ko`), the caller's code read through `platformLocaleTagOf` and then shortened one subtag at a time; an absent locale, or one the table does not name, is answered in English exactly as before. `ok`, `severity`, the probe and its cleanup, and the operator log lines are unchanged.
@@ -87,6 +87,7 @@ import { mayActIrreversibly } from '@objectstack/platform-objects/system';
 import { FILE_REFERENCES_MIGRATION_ID } from '@objectstack/spec/system';
 import { inProcessSessionReadInput } from '@objectstack/types';
 import { SwappableStorageService } from './swappable-storage-service.js';
+import { S3SettingsIncompleteError, storageTestCopy } from './storage-test-copy.js';
 import {
   resolveStorageTarget,
   needsStorageSwap,
@@ -286,7 +287,7 @@ export class StorageServicePlugin implements Plugin {
       const bucket = values.s3_bucket as string | undefined;
       const region = values.s3_region as string | undefined;
       if (!bucket || !region) {
-        throw new Error('StorageServicePlugin: S3 adapter requires s3_bucket and s3_region');
+        throw new S3SettingsIncompleteError();
       }
       const opts: S3StorageAdapterOptions = {
         bucket,
@@ -814,7 +815,11 @@ export class StorageServicePlugin implements Plugin {
         // Register the live `storage/test` probe handler.
         if (typeof settings.registerAction === 'function' && this.storage) {
           const proxy = this.storage;
-          settings.registerAction('storage', 'test', async ({ values, payload }: any) => {
+          settings.registerAction('storage', 'test', async ({ values, payload, locale }: any) => {
+            // [#30335] The answer is the toast the administrator reads: written
+            // in the caller's display language, which the settings action
+            // route hands over as `locale` (English when none is given).
+            const copy = storageTestCopy(typeof locale === 'string' ? locale : undefined);
             // Merge the (possibly unsaved) form state posted as
             // `payload.values` over the persisted snapshot so an operator
             // can validate edits before hitting "Save". Matches the
@@ -851,7 +856,10 @@ export class StorageServicePlugin implements Plugin {
               try {
                 target = await this.buildAdapterFromValues(merged);
               } catch (err: any) {
-                return { ok: false, severity: 'error', message: err?.message ?? String(err) };
+                const message = err instanceof S3SettingsIncompleteError
+                  ? copy.s3SettingsIncomplete
+                  : copy.failed(err?.message ?? String(err));
+                return { ok: false, severity: 'error', message };
               }
             }
 
@@ -900,18 +908,18 @@ export class StorageServicePlugin implements Plugin {
                 // unguarded delete, whose failure IS a probe failure the
                 // operator must be told about, and no path deletes twice.
                 await removeProbeObject();
-                return { ok: false, severity: 'error', message: 'Probe download did not match upload.' };
+                return { ok: false, severity: 'error', message: copy.downloadMismatch };
               }
               await target.delete(probeKey);
               const adapter = String(merged.adapter ?? this.options.adapter ?? 'local');
               return {
                 ok: true,
                 severity: 'info',
-                message: `Storage round-trip succeeded (adapter=${adapter}).`,
+                message: copy.succeeded(adapter),
               };
             } catch (err: any) {
               await removeProbeObject();
-              return { ok: false, severity: 'error', message: err?.message ?? String(err) };
+              return { ok: false, severity: 'error', message: copy.failed(err?.message ?? String(err)) };
             }
           });
           ctx.logger.info('StorageServicePlugin: registered settings action storage/test');
 
@@ -0,0 +1,161 @@
+// Copyright (c) 2025 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * [#30335] The sentences Setup → Storage → 测试连接 (`storage/test`) answers
+ * with, one entry per language on the platform locale table.
+ *
+ * The console prints the action's `message` as the toast, bare, so the
+ * sentence is the administrator's whole answer. The settings action route
+ * hands the handler the caller's display language (`Accept-Language`, else
+ * `?locale`) as the input's `locale`; an absent locale, or one with no entry
+ * here, is answered in English, the sentence every caller got before.
+ *
+ * The table carries every language on the platform locale table
+ * (`@objectstack/spec/system` `PLATFORM_LOCALES`). The four entries this package
+ * served first keep their keys (`zh-CN`, `ja-JP`, `es-ES`); the caller's code is
+ * read through the table's own reader, `platformLocaleTagOf`, so a stored
+ * alias (`zh-TW`, `pt`, `en-US`) and a table tag (`zh-Hans`, `ja`) both find
+ * their entry. A code the table does not name is shortened one subtag at a
+ * time (RFC 4647 lookup: `fr-CA` → `fr`, `zh-Hant-TW` → `zh-Hant`); nothing
+ * left ⇒ English.
+ *
+ * Only the sentences the product writes live here. An adapter's own error
+ * text (the S3 SDK's, the file system's) is passed through verbatim: in
+ * English on its own, as it always was; in another language behind a lead-in
+ * that says the connection test failed, so the reader knows what the
+ * untranslated part is. The operator log lines stay English.
+ */
+
+import { platformLocaleTagOf, type PlatformLocaleTag } from '@objectstack/spec/system';
+
+/** The English refusal for S3 settings missing a bucket or a region. */
+export const S3_SETTINGS_INCOMPLETE_MESSAGE =
+  'StorageServicePlugin: S3 adapter requires s3_bucket and s3_region';
+
+/**
+ * Thrown when the `storage` settings name the S3 adapter without a bucket or a
+ * region. Its message is the English refusal the operator log has always
+ * carried; the `storage/test` answer reads the type to write the refusal in the
+ * caller's language instead.
+ */
+export class S3SettingsIncompleteError extends Error {
+  constructor() {
+    super(S3_SETTINGS_INCOMPLETE_MESSAGE);
+    this.name = 'S3SettingsIncompleteError';
+  }
+}
+
+export interface StorageTestCopy {
+  /** The probe object was written, read back identical and deleted. */
+  succeeded(adapter: string): string;
+  /** The probe object read back is not the one written. */
+  downloadMismatch: string;
+  /** The S3 adapter was chosen without a bucket or a region. */
+  s3SettingsIncomplete: string;
+  /** The adapter refused; `reason` is its own text, verbatim. */
+  failed(reason: string): string;
+}
+
+/** The table's keys: the platform locale table's languages, the first four under their older codes. */
+export type StorageTestCopyLocale =
+  'en' | 'zh-CN' | 'zh-Hant' | 'es-ES' | 'ar' | 'fr' | 'pt-BR' | 'ru' | 'de' | 'ja-JP' | 'ko';
+
+export const STORAGE_TEST_COPY: Record<StorageTestCopyLocale, StorageTestCopy> = {
+  en: {
+    succeeded: (adapter) => `Storage round-trip succeeded (adapter=${adapter}).`,
+    downloadMismatch: 'Probe download did not match upload.',
+    s3SettingsIncomplete: S3_SETTINGS_INCOMPLETE_MESSAGE,
+    failed: (reason) => reason,
+  },
+  'zh-CN': {
+    succeeded: (adapter) => `存储连接测试成功（适配器：${adapter}）。`,
+    downloadMismatch: '探测文件下载后的内容与上传的不一致。',
+    s3SettingsIncomplete: 'S3 适配器需要填写存储桶（s3_bucket）和区域（s3_region）。',
+    failed: (reason) => `存储连接测试失败：${reason}`,
+  },
+  'zh-Hant': {
+    succeeded: (adapter) => `儲存空間連線測試成功（轉接器：${adapter}）。`,
+    downloadMismatch: '探測檔案下載後的內容與上傳的不一致。',
+    s3SettingsIncomplete: 'S3 轉接器需要填寫儲存貯體（s3_bucket）和區域（s3_region）。',
+    failed: (reason) => `儲存空間連線測試失敗：${reason}`,
+  },
+  'ja-JP': {
+    succeeded: (adapter) => `ストレージの接続テストに成功しました（アダプター: ${adapter}）。`,
+    downloadMismatch: 'プローブファイルのダウンロード内容がアップロードした内容と一致しません。',
+    s3SettingsIncomplete: 'S3 アダプターにはバケット（s3_bucket）とリージョン（s3_region）の指定が必要です。',
+    failed: (reason) => `ストレージの接続テストに失敗しました: ${reason}`,
+  },
+  ko: {
+    succeeded: (adapter) => `스토리지 연결 테스트에 성공했습니다(어댑터: ${adapter}).`,
+    downloadMismatch: '다운로드한 테스트 파일이 업로드한 파일과 일치하지 않습니다.',
+    s3SettingsIncomplete: 'S3 어댑터에는 버킷(s3_bucket)과 리전(s3_region)이 필요합니다.',
+    failed: (reason) => `스토리지 연결 테스트에 실패했습니다: ${reason}`,
+  },
+  'es-ES': {
+    succeeded: (adapter) => `La prueba de conexión del almacenamiento se ha completado correctamente (adaptador: ${adapter}).`,
+    downloadMismatch: 'El archivo de prueba descargado no coincide con el que se subió.',
+    s3SettingsIncomplete: 'El adaptador S3 necesita un bucket (s3_bucket) y una región (s3_region).',
+    failed: (reason) => `La prueba de conexión del almacenamiento ha fallado: ${reason}`,
+  },
+  ar: {
+    succeeded: (adapter) => `نجح اختبار الاتصال بالتخزين (المحوّل: ${adapter}).`,
+    downloadMismatch: 'محتوى ملف الاختبار الذي تم تنزيله لا يطابق الملف الذي تم رفعه.',
+    s3SettingsIncomplete: 'يتطلب محوّل S3 تحديد الحاوية (s3_bucket) والمنطقة (s3_region).',
+    failed: (reason) => `فشل اختبار الاتصال بالتخزين: ${reason}`,
+  },
+  fr: {
+    succeeded: (adapter) => `Le test de connexion au stockage a réussi (adaptateur : ${adapter}).`,
+    downloadMismatch: 'Le fichier de test téléchargé ne correspond pas à celui qui a été envoyé.',
+    s3SettingsIncomplete: 'L’adaptateur S3 nécessite un bucket (s3_bucket) et une région (s3_region).',
+    failed: (reason) => `Le test de connexion au stockage a échoué : ${reason}`,
+  },
+  'pt-BR': {
+    succeeded: (adapter) => `O teste de conexão com o armazenamento foi concluído com sucesso (adaptador: ${adapter}).`,
+    downloadMismatch: 'O arquivo de teste baixado não corresponde ao que foi enviado.',
+    s3SettingsIncomplete: 'O adaptador S3 exige um bucket (s3_bucket) e uma região (s3_region).',
+    failed: (reason) => `O teste de conexão com o armazenamento falhou: ${reason}`,
+  },
+  ru: {
+    succeeded: (adapter) => `Проверка подключения к хранилищу прошла успешно (адаптер: ${adapter}).`,
+    downloadMismatch: 'Скачанный тестовый файл не совпадает с загруженным.',
+    s3SettingsIncomplete: 'Для адаптера S3 нужно указать бакет (s3_bucket) и регион (s3_region).',
+    failed: (reason) => `Проверка подключения к хранилищу не удалась: ${reason}`,
+  },
+  de: {
+    succeeded: (adapter) => `Der Verbindungstest zum Speicher war erfolgreich (Adapter: ${adapter}).`,
+    downloadMismatch: 'Die heruntergeladene Testdatei stimmt nicht mit der hochgeladenen überein.',
+    s3SettingsIncomplete: 'Der S3-Adapter benötigt einen Bucket (s3_bucket) und eine Region (s3_region).',
+    failed: (reason) => `Der Verbindungstest zum Speicher ist fehlgeschlagen: ${reason}`,
+  },
+};
+
+/** Each platform locale table tag → the key that serves it. */
+const KEY_BY_TABLE_TAG: Record<PlatformLocaleTag, StorageTestCopyLocale> = {
+  en: 'en',
+  'zh-Hans': 'zh-CN',
+  'zh-Hant': 'zh-Hant',
+  es: 'es-ES',
+  ar: 'ar',
+  fr: 'fr',
+  'pt-BR': 'pt-BR',
+  ru: 'ru',
+  de: 'de',
+  ja: 'ja-JP',
+  ko: 'ko',
+};
+
+/** The key that serves a caller's code, or `undefined` (⇒ English). */
+export function storageTestCopyLocaleOf(locale: string | undefined): StorageTestCopyLocale | undefined {
+  if (!locale) return undefined;
+  const subtags = locale.split('-');
+  for (let n = subtags.length; n > 0; n -= 1) {
+    const tag = platformLocaleTagOf(subtags.slice(0, n).join('-'));
+    if (tag) return KEY_BY_TABLE_TAG[tag];
+  }
+  return undefined;
+}
+
+/** The copy for a caller's locale; English when the code names no language on the table. */
+export function storageTestCopy(locale: string | undefined): StorageTestCopy {
+  return STORAGE_TEST_COPY[storageTestCopyLocaleOf(locale) ?? 'en'];
+}