@@ -0,0 +1,18 @@
+---
+'@object-ui/react': patch
+---
+
+fix(react): an inline action's `description` locale map shows in the user's language in the param dialog
+
+Clause-②: no
+Metadata-protocol: none
+
+An inline action on a page (`element:button` with `properties.action`) can declare a `description`, the line its param dialog shows under the title. It may be written as a per-locale map such as `{ en: '…', 'zh-CN': '…' }`. Before this change the action text localizer left that map alone, so the dialog received an object instead of a sentence.
+
+What changes:
+
+- `useActionTextLocalizer` now collapses a declared `description` to the active language, the same way it already treats `confirmText`, `successMessage` and `errorMessage`. A plain string comes back unchanged, and a `{ dialect: 'template', source }` envelope comes back as itself.
+- It does not read a translation bundle entry for `description`. The param-dialog host still resolves `_actions.<name>.description` over the string it is handed.
+- An action that declares no `description` gains no key, so its dialog keeps the generic "Please provide the required information to continue." line.
+
+What to do: nothing. Nothing a page, view or action declares changes.
@@ -0,0 +1,156 @@
+/**
+ * ObjectUI
+ * Copyright (c) 2024-present ObjectStack Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * objectstack#29249 — an inline `element:button` action's `description`
+ * reaches the param dialog in the user's language.
+ *
+ * `InlineActionSchema` picks `description` (an `I18nLabel`: a string or a
+ * per-locale map). The button hands its action to `useActionTextLocalizer`
+ * before the runner, so a map collapses to the active language there; the
+ * runner and the param-collection host have no language of their own.
+ *
+ * The path is the real one up to the param-collection seam: the registered
+ * `element:button`, the real localizer, the real `ActionRunner` behind
+ * `ActionProvider`. The dialog is this file's host, drawn with this package's
+ * `Dialog` the way the console's `ActionParamDialog` (`@object-ui/app-shell`,
+ * which this package cannot import) draws its line: the action's description,
+ * else the generic `actionDialog.description`.
+ *
+ * Each row first asserts the dialog opened with the action's own title (the
+ * positive control), so a missing line is never "no dialog opened".
+ */
+
+import { describe, it, expect, vi, beforeEach, type Mock } from 'vitest';
+import { render, screen, fireEvent } from '@testing-library/react';
+import React from 'react';
+import { ComponentRegistry } from '@object-ui/core';
+import type { ActionContext, ActionDef, ActionResult, ParamCollectionHandler } from '@object-ui/core';
+import { ActionProvider } from '@object-ui/react';
+import { I18nProvider, useObjectTranslation } from '@object-ui/i18n';
+import { Dialog, DialogContent, DialogTitle, DialogDescription } from '../ui/dialog';
+import '../renderers/basic/elements';
+
+let api: Mock<(action: ActionDef, ctx: ActionContext) => Promise<ActionResult>>;
+let handed: Array<ActionDef | undefined>;
+
+beforeEach(() => {
+  api = vi.fn(async () => ({ success: true }));
+  handed = [];
+});
+
+/** The producer's shape: a nameless inline `api` action that collects params. */
+const INVITE = {
+  type: 'api',
+  target: '/api/v1/cloud/invitations',
+  label: { en: 'Invite member', 'zh-CN': '邀请成员' },
+  params: [{ name: 'email', label: 'Email', type: 'email', required: true }],
+};
+
+const DESCRIPTION = {
+  en: 'We e-mail them an invitation link.',
+  'zh-CN': '我们会向对方发送一封邀请邮件。',
+};
+
+/**
+ * The registered renderer, read once at module scope (a component created
+ * during render remounts on every render). An unregistered `element:button`
+ * fails the whole file here, before any row runs.
+ */
+function registeredElementButton() {
+  const C = ComponentRegistry.get('element:button');
+  if (!C) throw new Error('element:button not registered');
+  return C;
+}
+const ElementButton = registeredElementButton();
+
+/**
+ * The param-collection host: opens a dialog from what the runner hands it and
+ * leaves the promise pending, as a dialog awaiting its Confirm does.
+ */
+function ParamHost({ action }: { action: Record<string, unknown> }) {
+  const { t } = useObjectTranslation();
+  const [dialog, setDialog] = React.useState<{ title: string; description: string } | null>(null);
+  const onParamCollection = React.useCallback<ParamCollectionHandler>((_params, dispatched) => {
+    handed.push(dispatched);
+    // A non-string reaching the host is drawn as nothing, so the assertions
+    // below see the gap instead of React refusing an object child.
+    const title = dispatched?.label;
+    const description = dispatched?.description;
+    setDialog({
+      title: typeof title === 'string' ? title : '',
+      description: typeof description === 'string' ? description : '',
+    });
+    return new Promise(() => {});
+  }, []);
+  return (
+    <ActionProvider handlers={{ api }} onParamCollection={onParamCollection}>
+      <ElementButton
+        schema={{
+          type: 'element:button',
+          properties: { label: { en: 'Invite member', 'zh-CN': '邀请成员' }, action },
+        }}
+      />
+      {dialog && (
+        <Dialog open>
+          <DialogContent>
+            <DialogTitle>{dialog.title}</DialogTitle>
+            <DialogDescription>{dialog.description || t('actionDialog.description')}</DialogDescription>
+          </DialogContent>
+        </Dialog>
+      )}
+    </ActionProvider>
+  );
+}
+
+function renderIn(language: string, action: Record<string, unknown>) {
+  return render(
+    <I18nProvider config={{ defaultLanguage: language, detectBrowserLanguage: false }} persistLanguage={false}>
+      <ParamHost action={action} />
+    </I18nProvider>,
+  );
+}
+
+describe('element:button — the param dialog shows the inline description in the active language (objectstack#29249)', () => {
+  it('a zh-CN/en map shows the zh-CN string under a zh-CN locale', async () => {
+    renderIn('zh-CN', { ...INVITE, description: DESCRIPTION });
+
+    fireEvent.click(screen.getByRole('button', { name: '邀请成员' }));
+
+    const dialog = await screen.findByRole('dialog');
+    expect(screen.getByRole('heading', { name: '邀请成员' })).toBeTruthy();
+    expect(dialog.textContent).toContain('我们会向对方发送一封邀请邮件。');
+    // The runner was handed one string, never the map.
+    expect(handed).toHaveLength(1);
+    expect(handed[0]?.description).toBe('我们会向对方发送一封邀请邮件。');
+    // Nothing runs until the dialog's own Confirm.
+    expect(api).not.toHaveBeenCalled();
+  });
+
+  it('the same map shows the English string under an en locale', async () => {
+    renderIn('en', { ...INVITE, description: DESCRIPTION });
+
+    fireEvent.click(screen.getByRole('button', { name: 'Invite member' }));
+
+    const dialog = await screen.findByRole('dialog');
+    expect(screen.getByRole('heading', { name: 'Invite member' })).toBeTruthy();
+    expect(dialog.textContent).toContain('We e-mail them an invitation link.');
+    expect(handed[0]?.description).toBe('We e-mail them an invitation link.');
+  });
+
+  it('no description: the dialog keeps its generic line', async () => {
+    renderIn('zh-CN', INVITE);
+
+    fireEvent.click(screen.getByRole('button', { name: '邀请成员' }));
+
+    const dialog = await screen.findByRole('dialog');
+    expect(screen.getByRole('heading', { name: '邀请成员' })).toBeTruthy();
+    expect(dialog.textContent).toContain('请填写以下信息以继续操作。');
+    expect(handed[0]?.description).toBeUndefined();
+  });
+});
@@ -0,0 +1,113 @@
+/**
+ * ObjectUI
+ * Copyright (c) 2024-present ObjectStack Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * objectstack#29249 — an action's `description`, the line the param dialog
+ * draws under its title, is declared `I18nLabel` copy like `confirmText`: an
+ * inline per-locale map collapses to the active language before the runner
+ * and the dialog, which have no language, receive it.
+ *
+ * Declared-only and collapse-only, like `errorMessage`: an action that
+ * declares no `description` gains no key (the dialog keeps its generic line),
+ * and the bundle's `_actions.<name>.description` is not read here — the
+ * param-collection host resolves that entry over the string handed on.
+ *
+ * Measured under a real `I18nProvider`, reading what the localizer returns.
+ */
+import { describe, it, expect, afterEach } from 'vitest';
+import { cleanup, renderHook } from '@testing-library/react';
+import React from 'react';
+import { I18nProvider, useObjectTranslation } from '@object-ui/i18n';
+import { useActionTextLocalizer } from '../useActionTextLocalizer';
+
+afterEach(() => cleanup());
+
+const DESCRIPTION = {
+  en: 'We e-mail them an invitation link.',
+  'zh-CN': '我们会向对方发送一封邀请邮件。',
+};
+
+/** The producer's shape: a nameless inline `api` action that collects params. */
+const INVITE = {
+  type: 'api',
+  target: '/api/v1/cloud/invitations',
+  label: { en: 'Invite member', 'zh-CN': '邀请成员' },
+  params: [{ name: 'email', label: 'Email', type: 'email', required: true }],
+};
+
+function harness(language: string, bundle?: Record<string, unknown>) {
+  const wrapper = ({ children }: { children: React.ReactNode }) => (
+    <I18nProvider config={{ defaultLanguage: language, detectBrowserLanguage: false }} persistLanguage={false}>
+      {children}
+    </I18nProvider>
+  );
+  const { result } = renderHook(
+    () => ({ localize: useActionTextLocalizer(), translation: useObjectTranslation() }),
+    { wrapper },
+  );
+  if (bundle) result.current.translation.i18n.addResourceBundle(language, 'translation', bundle, true, true);
+  return result;
+}
+
+describe('useActionTextLocalizer — description (objectstack#29249)', () => {
+  it('a nameless inline action: the locale map collapses to the zh-CN string', () => {
+    const result = harness('zh-CN');
+    const localized = result.current.localize(undefined, { ...INVITE, description: DESCRIPTION });
+    expect(localized.description).toBe('我们会向对方发送一封邀请邮件。');
+  });
+
+  it('the same map reads the English entry under an en locale', () => {
+    const result = harness('en');
+    const localized = result.current.localize(undefined, { ...INVITE, description: DESCRIPTION });
+    expect(localized.description).toBe('We e-mail them an invitation link.');
+  });
+
+  it('a named action collapses the map too, and the bundle entry is not read here', () => {
+    const result = harness('zh-CN', {
+      sys: { globalActions: { invite_member: { label: '邀请同事', description: '来自翻译包的说明' } } },
+    });
+    const localized = result.current.localize(undefined, {
+      ...INVITE,
+      name: 'invite_member',
+      description: DESCRIPTION,
+    });
+    // Positive control: the same bundle node IS read for `label`, so the
+    // harness reached a named action's bundle path.
+    expect(localized.label).toBe('邀请同事');
+    // Collapse-only: the host's `actionDescription` owns the bundle read.
+    expect(localized.description).toBe('我们会向对方发送一封邀请邮件。');
+  });
+
+  it('a `template` envelope comes back as itself, never collapsed as a locale map', () => {
+    const result = harness('zh-CN');
+    const envelope = { dialect: 'template', source: 'Invite {{ record.name }} to the team.' };
+    const action = { ...INVITE, label: 'Invite member', description: envelope };
+    const localized = result.current.localize(undefined, action);
+    expect(localized.description).toBe(envelope);
+    expect(localized.description).toEqual({ dialect: 'template', source: 'Invite {{ record.name }} to the team.' });
+  });
+
+  it('a plain string comes back unchanged', () => {
+    const result = harness('zh-CN');
+    const localized = result.current.localize(undefined, {
+      ...INVITE,
+      description: 'We e-mail them an invitation link.',
+    });
+    expect(localized.description).toBe('We e-mail them an invitation link.');
+  });
+
+  it('an action with no description gains no key, nameless or named', () => {
+    const result = harness('zh-CN', {
+      sys: { globalActions: { invite_member: { description: '来自翻译包的说明' } } },
+    });
+    const nameless = result.current.localize(undefined, INVITE);
+    const named = result.current.localize(undefined, { ...INVITE, name: 'invite_member' });
+    expect('description' in nameless).toBe(false);
+    expect('description' in named).toBe(false);
+  });
+});
@@ -62,14 +62,22 @@
  *   declares resolves `_actions.<name>.outcomeMessages.<outcome>`; a bundle
  *   entry for an outcome the action does not declare is never read, so a
  *   bundle cannot add copy for an answer the author never wrote one for.
- * - **`label`, `confirmText`, `successMessage`, `errorMessage` and each
- *   `outcomeMessages` entry are reduced through `pickLocalized` first**,
- *   because each is an `I18nLabel` — a string or an inline per-locale map. The map is collapsed to the active language
+ * - **`label`, `confirmText`, `successMessage`, `errorMessage`, `description`
+ *   and each `outcomeMessages` entry are reduced through `pickLocalized`
+ *   first**, because each is an `I18nLabel` — a string or an inline per-locale map. The map is collapsed to the active language
  *   BEFORE it is offered to the bundle as the fallback, so a per-locale
  *   literal and a bundle entry cannot disagree about what "the authored text"
  *   is, and the action runner, which has no language, only ever receives a
  *   string. `errorMessage` has no bundle key (the spec's action translation
  *   declares none), so the collapse is all it gets (objectui#12757).
+ * - **`description` is collapse-only too** (objectstack#29249): the line the
+ *   param dialog draws under its title is an `I18nLabel` on an inline action
+ *   (`InlineActionSchema` picks it), so a locale map collapses to the active
+ *   language here, before the runner and the dialog, which have no language,
+ *   receive it. Its bundle entry (`_actions.<name>.description`) is NOT read
+ *   here: the param-collection host resolves it (`actionDescription` in
+ *   `useConsoleActionRuntime`), over the string this hook hands on. An action
+ *   that declares none gains no key, so the dialog keeps its generic line.
  * - **`disabledReason` follows the same declared-only rule**
  *   (objectstack#26619): the reason a greyed action gives resolves
  *   `_actions.<name>.disabledReason` only when the action declares one, after
@@ -90,7 +98,8 @@
  *   scope `onSuccess.navigate` reads — one interpolation, in one place.
  * - **The `template` envelope keeps its shape** (objectui#13367, the renderer
  *   half of objectstack#24814). `confirmText`, `successMessage`,
- *   `errorMessage` and each `outcomeMessages` entry (objectstack#27948) may
+ *   `errorMessage`, `description` and each `outcomeMessages` entry
+ *   (objectstack#27948) may
  *   arrive as `{ dialect: 'template', source }` instead of a string. The
  *   envelope is not an `I18nLabel` map — read as one it would
  *   collapse to its first string value, the word `template` — so its `source`
@@ -113,10 +122,11 @@ export interface ActionTextLocalizerOptions {
 
 /**
  * Returns a copy of `action` with `label` — plus `confirmText`,
- * `successMessage`, `errorMessage`, `outcomeMessages`, `disabledReason` and
- * `cancelText` when the action declares them —
+ * `successMessage`, `errorMessage`, `description`, `outcomeMessages`,
+ * `disabledReason` and `cancelText` when the action declares them —
  * resolved from the active locale's bundle, falling back to the authored
- * literals. `objectName` is the host object the action is drawn on; the
+ * literals (`errorMessage` and `description` are collapsed to the active
+ * language only; neither reads the bundle here). `objectName` is the host object the action is drawn on; the
  * action's own declared `objectName` wins over it when present.
  */
 export type ActionTextLocalizer = <T extends Record<string, any>>(
@@ -126,7 +136,7 @@ export type ActionTextLocalizer = <T extends Record<string, any>>(
 ) => T;
 
 /** The declared `I18nLabel` copy, besides `label`, that reaches the runner. */
-const DECLARED_COPY_KEYS = ['confirmText', 'successMessage', 'errorMessage'] as const;
+const DECLARED_COPY_KEYS = ['confirmText', 'successMessage', 'errorMessage', 'description'] as const;
 
 /**
  * Collapse one declared copy value to the active language: an `I18nLabel`