diff --git a/.changeset/plugin-audit-summary-i18n-3039.md b/.changeset/plugin-audit-summary-i18n-3039.md
new file mode 100644
index 0000000000..40d69d2513
--- /dev/null
+++ b/.changeset/plugin-audit-summary-i18n-3039.md
@@ -0,0 +1,13 @@
+---
+'@objectstack/plugin-audit': patch
+---
+
+Localize activity summaries to the workspace default locale (#3039). Activity
+writers previously hardcoded English verbs and the object API name
+(`Created person_qualification "OC-00001"`). The writer now resolves the
+ADR-0053 `localization.locale` setting per write (memoized per tenant/user
+scope), renders the verb through new `messages.activityCreated/Updated/Deleted`
+i18n templates (en, zh-CN, ja-JP, es-ES shipped), and names the object by its
+localized label (`objects.{name}.label`) with fallback to the authored def
+label, then the API name. Missing i18n/settings services or bundle keys
+degrade to the previous English summaries.
diff --git a/packages/plugins/plugin-audit/src/audit-plugin.ts b/packages/plugins/plugin-audit/src/audit-plugin.ts
index 16d782937a..b305a873fd 100644
--- a/packages/plugins/plugin-audit/src/audit-plugin.ts
+++ b/packages/plugins/plugin-audit/src/audit-plugin.ts
@@ -1,6 +1,7 @@
 // Copyright (c) 2025 ObjectStack. Licensed under the Apache-2.0 license.
 
 import type { Plugin, PluginContext } from '@objectstack/core';
+import { resolveLocalizationContext } from '@objectstack/core';
 import type { IDataEngine } from '@objectstack/spec/contracts';
 import { SysAuditLog, SysActivity, SysComment } from './objects/index.js';
 // `sys_notification` is contributed here but owned by platform-objects; it is
@@ -9,7 +10,7 @@ import { SysAuditLog, SysActivity, SysComment } from './objects/index.js';
 // storage (ADR-0052 §3 ownership: a file↔record link belongs with storage, not
 // the compliance ledger).
 import { SysNotification } from '@objectstack/platform-objects/audit';
-import { installAuditWriters, type MessagingEmitSurface } from './audit-writers.js';
+import { installAuditWriters, type AuditI18nSurface, type MessagingEmitSurface } from './audit-writers.js';
 
 /**
  * AuditPlugin
@@ -108,7 +109,27 @@ export class AuditPlugin implements Plugin {
           return undefined;
         }
       };
-      installAuditWriters(engine as any, this.name, { getMessaging });
+      // framework#3039 — localize activity summaries to the workspace default
+      // locale (ADR-0053 `localization.locale`). Both seams resolve lazily and
+      // tolerate absence: no i18n / no settings degrades to English summaries.
+      const getI18n = (): AuditI18nSurface | undefined => {
+        try {
+          return ctx.getService<AuditI18nSurface>('i18n');
+        } catch {
+          return undefined;
+        }
+      };
+      const getLocale = async (tenantId?: string, userId?: string): Promise<string | undefined> => {
+        let settings: unknown;
+        try {
+          settings = ctx.getService('settings');
+        } catch {
+          settings = undefined;
+        }
+        const { locale } = await resolveLocalizationContext({ ql: engine, settings, tenantId, userId });
+        return locale;
+      };
+      installAuditWriters(engine as any, this.name, { getMessaging, getI18n, getLocale });
       process.stderr.write('[AuditPlugin] writers installed\n');
       ctx.logger.info('AuditPlugin: audit + activity writers installed');
     });
diff --git a/packages/plugins/plugin-audit/src/audit-writers.test.ts b/packages/plugins/plugin-audit/src/audit-writers.test.ts
index 7aa750de91..acd497ac35 100644
--- a/packages/plugins/plugin-audit/src/audit-writers.test.ts
+++ b/packages/plugins/plugin-audit/src/audit-writers.test.ts
@@ -439,3 +439,105 @@ describe('audit writers — enable.files server-side enforcement (#2727)', () =>
     await expect(fire('beforeInsert', attachmentInsert(undefined))).resolves.toBeUndefined();
   });
 });
+
+describe('audit writers — localized activity summaries (framework#3039)', () => {
+  // Real memory i18n (what the kernel registers as the 'i18n' fallback) loaded
+  // with this plugin's shipped bundle plus an app-contributed object label —
+  // exercises the actual key shapes (`messages.activityCreated`,
+  // `objects.{name}.label`) end to end.
+  async function makeI18n() {
+    const { createMemoryI18n } = await import('@objectstack/core');
+    const { AuditTranslations } = await import('./translations/index.js');
+    const i18n = createMemoryI18n();
+    for (const [locale, data] of Object.entries(AuditTranslations)) {
+      i18n.loadTranslations(locale, data as Record<string, any>);
+    }
+    i18n.loadTranslations('zh-CN', {
+      objects: { person_qualification: { label: '人员资质' } },
+    });
+    return i18n;
+  }
+
+  function setup(
+    locale: string | undefined,
+    i18n?: { t: Function },
+    objectDefs: Record<string, any> = {},
+    schemas: Record<string, string[] | Record<string, any>> = SINGLE_TENANT,
+  ) {
+    const { engine, fire, created } = makeEngine(schemas, objectDefs);
+    let localeCalls = 0;
+    installAuditWriters(engine as any, 'test.audit', {
+      getI18n: () => i18n as any,
+      getLocale: async () => {
+        localeCalls += 1;
+        return locale;
+      },
+    });
+    return { fire, created, localeCalls: () => localeCalls };
+  }
+
+  const insertCtx = (object = 'person_qualification') => ({
+    object,
+    input: { id: 'q-1' },
+    result: { id: 'q-1', name: 'OC-00001' },
+    session: { tenantId: 'org-1', userId: 'user-1' },
+  });
+
+  it('localizes verb + object label to the workspace locale (zh-CN)', async () => {
+    const { fire, created } = setup('zh-CN', await makeI18n());
+
+    await fire('afterInsert', insertCtx());
+    await fire('afterDelete', { ...insertCtx(), result: null, __previous: { id: 'q-1', name: 'OC-00001' } });
+
+    const summaries = created.filter((c) => c.object === 'sys_activity').map((c) => c.row.summary);
+    expect(summaries).toEqual(['创建了 人员资质 "OC-00001"', '删除了 人员资质 "OC-00001"']);
+  });
+
+  it('localizes the generic update fallback', async () => {
+    const { fire, created } = setup('zh-CN', await makeI18n());
+    await fire('afterUpdate', {
+      ...insertCtx(),
+      __previous: { id: 'q-1', name: 'OC-00001', status: 'draft' },
+      result: { id: 'q-1', name: 'OC-00001', status: 'active' },
+    });
+    const activity = created.find((c) => c.object === 'sys_activity');
+    expect(activity!.row.summary).toBe('更新了 人员资质 "OC-00001"');
+  });
+
+  it('falls back to the object def label, then English, when a translation misses', async () => {
+    // Locale resolves but the object has no zh-CN label entry → verb is
+    // localized, label falls back to the authored def label.
+    const { fire, created } = setup(
+      'zh-CN',
+      await makeI18n(),
+      { crm_lead: { label: 'Lead' } },
+      { ...SINGLE_TENANT, crm_lead: ['id', 'name'] },
+    );
+    await fire('afterInsert', { ...insertCtx('crm_lead'), result: { id: 'q-1', name: 'Acme' } });
+    expect(created.find((c) => c.object === 'sys_activity')!.row.summary).toBe('创建了 Lead "Acme"');
+  });
+
+  it('keeps English summaries when no i18n service is resolvable', async () => {
+    const { fire, created } = setup('zh-CN', undefined);
+    await fire('afterInsert', insertCtx());
+    expect(created.find((c) => c.object === 'sys_activity')!.row.summary).toBe(
+      'Created person_qualification "OC-00001"',
+    );
+  });
+
+  it('keeps English summaries without a locale resolver (status quo)', async () => {
+    const { engine, fire, created } = makeEngine(SINGLE_TENANT);
+    installAuditWriters(engine as any, 'test.audit', { getI18n: () => undefined });
+    await fire('afterInsert', insertCtx());
+    expect(created.find((c) => c.object === 'sys_activity')!.row.summary).toBe(
+      'Created person_qualification "OC-00001"',
+    );
+  });
+
+  it('memoizes the locale lookup per tenant/user scope (hot-path guard)', async () => {
+    const { fire, localeCalls } = setup('zh-CN', await makeI18n());
+    await fire('afterInsert', insertCtx());
+    await fire('afterInsert', { ...insertCtx(), result: { id: 'q-2', name: 'OC-00002' } });
+    expect(localeCalls()).toBe(1);
+  });
+});
diff --git a/packages/plugins/plugin-audit/src/audit-writers.ts b/packages/plugins/plugin-audit/src/audit-writers.ts
index 749cf7d839..994186f2d2 100644
--- a/packages/plugins/plugin-audit/src/audit-writers.ts
+++ b/packages/plugins/plugin-audit/src/audit-writers.ts
@@ -22,6 +22,17 @@ export interface MessagingEmitSurface {
   }): Promise<unknown>;
 }
 
+/**
+ * Minimal structural view of `II18nService.t`. Declared locally (same
+ * rationale as {@link MessagingEmitSurface}) so plugin-audit resolves whatever
+ * object is registered under the `i18n` service without a runtime dependency
+ * on service-i18n. The kernel always registers at least the in-memory
+ * fallback, and `t` returns the key verbatim on a miss.
+ */
+export interface AuditI18nSurface {
+  t(key: string, locale: string, params?: Record<string, unknown>): string;
+}
+
 /** Options for {@link installAuditWriters}. */
 export interface AuditWriterOptions {
   /**
@@ -32,6 +43,19 @@ export interface AuditWriterOptions {
    * matching the `notify` node's degradation.
    */
   getMessaging?(): MessagingEmitSurface | undefined;
+  /**
+   * Lazily resolve the i18n service used to localize activity summaries
+   * (framework#3039): verb templates (`messages.activityCreated` …) and object
+   * display labels (`objects.{name}.label`). Absent → English summaries.
+   */
+  getI18n?(): AuditI18nSurface | undefined;
+  /**
+   * Resolve the workspace default locale (ADR-0053 `localization.locale`) for
+   * the write's tenant/user scope. Called per audited write but memoized here
+   * with a short TTL, so implementations may hit the settings service
+   * directly. Absent → summaries stay English (status quo).
+   */
+  getLocale?(tenantId?: string, userId?: string): Promise<string | undefined>;
 }
 
 /**
@@ -244,6 +268,28 @@ export function installAuditWriters(
   if (!engine || typeof engine.registerHook !== 'function') return;
 
   const getMessaging = opts.getMessaging ?? (() => undefined);
+  const getI18n = opts.getI18n ?? (() => undefined);
+
+  // Workspace locale changes rarely, but writeAudit runs on every CRUD write —
+  // memoize the settings lookup per principal scope with a short TTL so audit
+  // logging doesn't add a settings query to every mutation's hot path.
+  const LOCALE_TTL_MS = 30_000;
+  const localeCache = new Map<string, { value: string | undefined; expires: number }>();
+  const resolveWriteLocale = async (tenantId?: string, userId?: string): Promise<string | undefined> => {
+    if (!opts.getLocale) return undefined;
+    const cacheKey = `${tenantId ?? ''}|${userId ?? ''}`;
+    const now = Date.now();
+    const hit = localeCache.get(cacheKey);
+    if (hit && hit.expires > now) return hit.value;
+    let value: string | undefined;
+    try {
+      value = await opts.getLocale(tenantId, userId);
+    } catch {
+      value = undefined;
+    }
+    localeCache.set(cacheKey, { value, expires: now + LOCALE_TTL_MS });
+    return value;
+  };
 
   // Remove any prior installation so we can safely re-install on hot reload.
   if (typeof engine.unregisterHooksByPackage === 'function') {
@@ -449,19 +495,39 @@ export function installAuditWriters(
     const label = recordLabel(after ?? before, recordId ?? '');
     // Summaries are user-facing (the record Discussion feed and Setup
     // dashboards render them verbatim), so name the object by its display
-    // label ("Semantic Zoo"), not its API name ("showcase_semantic_zoo").
-    // Best-effort: falls back to the API name when the def isn't resolvable.
+    // label ("Semantic Zoo"), not its API name ("showcase_semantic_zoo"), and
+    // localize both the verb template and the object label to the workspace
+    // default locale (ADR-0053, framework#3039). Every step is best-effort:
+    // no locale / no i18n / key miss all degrade to the English literal.
+    const locale = await resolveWriteLocale(tenantId, userId);
+    const translate = (key: string, params?: Record<string, unknown>): string | undefined => {
+      if (!locale) return undefined;
+      const i18n = getI18n();
+      if (!i18n || typeof i18n.t !== 'function') return undefined;
+      try {
+        const value = i18n.t(key, locale, params);
+        // A miss returns the key verbatim (II18nService contract).
+        return typeof value === 'string' && value !== key ? value : undefined;
+      } catch {
+        return undefined;
+      }
+    };
     const objectDef = getObjectDef(ctx.object);
     const objectDisplay =
-      typeof objectDef?.label === 'string' && objectDef.label.length > 0
+      translate(`objects.${ctx.object}.label`) ??
+      (typeof objectDef?.label === 'string' && objectDef.label.length > 0
         ? objectDef.label
-        : ctx.object;
+        : ctx.object);
     let summary: string;
     let activityType: string = activityTypeFor(action);
     if (action === 'create') {
-      summary = `Created ${objectDisplay} "${label}"`;
+      summary =
+        translate('messages.activityCreated', { object: objectDisplay, label }) ??
+        `Created ${objectDisplay} "${label}"`;
     } else if (action === 'delete') {
-      summary = `Deleted ${objectDisplay} "${label}"`;
+      summary =
+        translate('messages.activityDeleted', { object: objectDisplay, label }) ??
+        `Deleted ${objectDisplay} "${label}"`;
     } else {
       // ADR-0052 §5b — declarative activity, precedence: a configured semantic
       // milestone (§5b.2) wins; else a tracked field-change diff ("Stage:
@@ -473,6 +539,7 @@ export function installAuditWriters(
       } else {
         summary =
           renderTrackedChangeSummary(getFieldDefs(ctx.object), oldValue, newValue) ??
+          translate('messages.activityUpdated', { object: objectDisplay, label }) ??
           `Updated ${objectDisplay} "${label}"`;
       }
     }
diff --git a/packages/plugins/plugin-audit/src/translations/index.ts b/packages/plugins/plugin-audit/src/translations/index.ts
index a90f97e45d..0d7f606c31 100644
--- a/packages/plugins/plugin-audit/src/translations/index.ts
+++ b/packages/plugins/plugin-audit/src/translations/index.ts
@@ -15,10 +15,11 @@ import { enObjects } from './en.objects.generated.js';
 import { zhCNObjects } from './zh-CN.objects.generated.js';
 import { jaJPObjects } from './ja-JP.objects.generated.js';
 import { esESObjects } from './es-ES.objects.generated.js';
+import { enMessages, zhCNMessages, jaJPMessages, esESMessages } from './messages.js';
 
 export const AuditTranslations: TranslationBundle = {
-  en: { objects: enObjects },
-  'zh-CN': { objects: zhCNObjects },
-  'ja-JP': { objects: jaJPObjects },
-  'es-ES': { objects: esESObjects },
+  en: { objects: enObjects, messages: enMessages },
+  'zh-CN': { objects: zhCNObjects, messages: zhCNMessages },
+  'ja-JP': { objects: jaJPObjects, messages: jaJPMessages },
+  'es-ES': { objects: esESObjects, messages: esESMessages },
 };
diff --git a/packages/plugins/plugin-audit/src/translations/messages.ts b/packages/plugins/plugin-audit/src/translations/messages.ts
new file mode 100644
index 0000000000..717355a878
--- /dev/null
+++ b/packages/plugins/plugin-audit/src/translations/messages.ts
@@ -0,0 +1,39 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * Activity summary verb templates (framework#3039).
+ *
+ * Keys are single-segment on purpose: both i18n implementations (the core
+ * memory fallback and service-i18n's FileI18nAdapter) resolve dot-notation
+ * keys by walking NESTED objects, so a flat record key containing a dot
+ * (`'activity.created'`) would never resolve — `messages.activityCreated`
+ * does. Interpolation uses the shared `{{param}}` convention.
+ */
+
+import type { TranslationData } from '@objectstack/spec/system';
+
+type Messages = NonNullable<TranslationData['messages']>;
+
+export const enMessages: Messages = {
+  activityCreated: 'Created {{object}} "{{label}}"',
+  activityUpdated: 'Updated {{object}} "{{label}}"',
+  activityDeleted: 'Deleted {{object}} "{{label}}"',
+};
+
+export const zhCNMessages: Messages = {
+  activityCreated: '创建了 {{object}} "{{label}}"',
+  activityUpdated: '更新了 {{object}} "{{label}}"',
+  activityDeleted: '删除了 {{object}} "{{label}}"',
+};
+
+export const jaJPMessages: Messages = {
+  activityCreated: '{{object}}「{{label}}」を作成しました',
+  activityUpdated: '{{object}}「{{label}}」を更新しました',
+  activityDeleted: '{{object}}「{{label}}」を削除しました',
+};
+
+export const esESMessages: Messages = {
+  activityCreated: 'Creó {{object}} "{{label}}"',
+  activityUpdated: 'Actualizó {{object}} "{{label}}"',
+  activityDeleted: 'Eliminó {{object}} "{{label}}"',
+};