@@ -0,0 +1,12 @@
+---
+'@objectstack/spec': patch
+---
+
+feat(spec/system): export the platform locale table `PLATFORM_LOCALES` and its read aliases
+
+Clause-②: yes (widening)
+Metadata-protocol: none
+
+- **`PLATFORM_LOCALES`** (from `@objectstack/spec/system`): the one list of languages the platform supports, as frozen rows `{ tag, label, rtl }` in menu order: `en`, `zh-Hans`, `zh-Hant`, `es`, `ar` (right to left), `fr`, `pt-BR`, `ru`, `de`, `ja`, `ko`, each labelled with its own native name. `PLATFORM_LOCALE_TAGS` is the tag list and `PlatformLocaleTag` the literal union of the tags.
+- **`PLATFORM_LOCALE_READ_ALIASES`** (typed on its ten literal keys, `PlatformLocaleReadAlias`) and **`platformLocaleTagOf(code)`**: the codes stored values already carry, mapped to the table tag they mean (`zh`, `zh-CN`, `zh-SG` to `zh-Hans`; `zh-TW`, `zh-HK`, `zh-MO` to `zh-Hant`; `ja-JP` to `ja`; `es-ES` to `es`; `pt` to `pt-BR`; `en-US` to `en`). A table tag answers itself and the match ignores case (`zh-cn` reads as `zh-Hans`). Any other code answers `undefined`; no region fallback is guessed.
+- The table is the target every surface is backfilled to; today the Console ships ten packs without `zh-Hant`, and platform metadata and the built-in emails ship four locales. Nothing reads the table yet and no schema refuses a tag that is not on it: every locale value that parsed before still parses. The protocol page `i18n-standard` gains the table, the read aliases and the rule (same-PR follow; a language is added or removed by changing the table and backfilling once).
@@ -125,6 +125,72 @@ Examples:
 - `zh-CN` — Chinese (Simplified, China)
 - `zh-TW` — Chinese (Traditional, Taiwan)
 
+### Platform Locale Table
+
+The platform supports **one** list of languages, exported from
+`@objectstack/spec/system` as `PLATFORM_LOCALES` (rows `{ tag, label, rtl }`,
+in menu order) with its tags as `PLATFORM_LOCALE_TAGS`. There are no tiers.
+The table is the rule every surface is held to: the Console UI, platform
+metadata and the built-in emails each carry every language on it.
+
+<Callout type="warn">
+**The target, not yet the state.** Today the Console ships ten packs (`en`,
+`zh`, `es`, `ar`, `fr`, `pt`, `ru`, `de`, `ja`, `ko`; no `zh-Hant`), platform
+metadata ships four locales (`en`, `zh-CN`, `ja-JP`, `es-ES`) and the built-in
+emails four (`en-US`, `zh-CN`, `ja-JP`, `es-ES`, with `en-US` as the floor).
+The surfaces are backfilled to the table in later phases.
+</Callout>
+
+| Language | Tag | Right to left |
+|:--|:--|:--|
+| English | `en` | |
+| 简体中文 | `zh-Hans` | |
+| 繁體中文 | `zh-Hant` | |
+| Español | `es` | |
+| العربية | `ar` | yes |
+| Français | `fr` | |
+| Português (Brasil) | `pt-BR` | |
+| Русский | `ru` | |
+| Deutsch | `de` | |
+| 日本語 | `ja` | |
+| 한국어 | `ko` | |
+
+The rule:
+
+- **Same-PR follow.** A change that adds a translatable string adds it for every
+  language its surface carries, in the same pull request; once a surface is
+  backfilled, that is every language on the table.
+- **Adding or removing a language** is a change to the table, followed by one
+  backfill of every surface. Nothing else declares the list.
+
+**Read aliases.** Codes that stored values already carry keep resolving:
+`PLATFORM_LOCALE_READ_ALIASES` maps each to a table tag, and
+`platformLocaleTagOf(code)` answers the table tag a stored code means.
+
+| Stored code | Reads as |
+|:--|:--|
+| `zh`, `zh-CN`, `zh-SG` | `zh-Hans` |
+| `zh-TW`, `zh-HK`, `zh-MO` | `zh-Hant` |
+| `ja-JP` | `ja` |
+| `es-ES` | `es` |
+| `pt` | `pt-BR` |
+| `en-US` | `en` |
+
+A table tag answers itself, the match ignores case (`zh-cn` reads as
+`zh-Hans`), and any other code answers `undefined`: no region fallback is
+guessed, so `pt-PT` is not `pt-BR`. New writes use the table's tags. The
+examples on this page that spell `zh-CN` stay valid, because `zh-CN` is a read
+alias of `zh-Hans`.
+
+`platformLocaleTagOf` answers which table language a code *means*; the
+fallback ladder below answers which key of a bundle *serves* a request. A
+reader that uses both maps the code first and then resolves the table tag
+against the bundle, so they do not contradict each other: `pt` means `pt-BR`,
+and a request for `pt-BR` may still be served by a bundle's `pt` key. The
+ladder alone cannot tell the two Chinese scripts apart: once a bundle holds
+both `zh-Hans` and `zh-Hant`, a request for `zh` or `zh-CN` is answered by key
+order (`zh-Hant` when that key comes first), where the table says `zh-Hans`.
+
 ### Locale Fallback
 
 If exact locale not found, ObjectStack falls back to **language-only** locale:
 
@@ -513,6 +513,9 @@
     "PAGE_FORM_COMPONENT_TYPE (const)",
     "PAGE_TABS_COMPONENT_TYPE (const)",
     "PKG_CONVENTIONS (const)",
+    "PLATFORM_LOCALES (const)",
+    "PLATFORM_LOCALE_READ_ALIASES (const)",
+    "PLATFORM_LOCALE_TAGS (const)",
     "PLATFORM_OBJECTS_BY_PACKAGE (const)",
     "PLATFORM_OBJECT_PREFIXES (const)",
     "PLATFORM_PROVIDED_OBJECT_NAMES (const)",
@@ -533,6 +536,9 @@
     "Plan (type)",
     "PlanParsed (type)",
     "PlanSchema (const)",
+    "PlatformLocale (interface)",
+    "PlatformLocaleReadAlias (type)",
+    "PlatformLocaleTag (type)",
     "PlatformTranslationBundle (type)",
     "PlatformTranslationBundleSchema (const)",
     "PlatformTranslationData (type)",
@@ -876,6 +882,7 @@
     "operationMessageTranslationKey (function)",
     "organizationOwnershipShapeGenerationOf (function)",
     "pageTabItemKey (function)",
+    "platformLocaleTagOf (function)",
     "preferredLocaleFromHeader (function)",
     "renderOperationMessage (function)",
     "renderValidationMessage (function)",
 
@@ -492,6 +492,9 @@
     "PAGE_FORM_COMPONENT_TYPE": "src/system/i18n-resolver.ts#PAGE_FORM_COMPONENT_TYPE (const)",
     "PAGE_TABS_COMPONENT_TYPE": "src/system/i18n-resolver.ts#PAGE_TABS_COMPONENT_TYPE (const)",
     "PKG_CONVENTIONS": "src/system/constants/paths.ts#PKG_CONVENTIONS (const)",
+    "PLATFORM_LOCALES": "src/system/platform-locales.ts#PLATFORM_LOCALES (const)",
+    "PLATFORM_LOCALE_READ_ALIASES": "src/system/platform-locales.ts#PLATFORM_LOCALE_READ_ALIASES (const)",
+    "PLATFORM_LOCALE_TAGS": "src/system/platform-locales.ts#PLATFORM_LOCALE_TAGS (const)",
     "PLATFORM_OBJECTS_BY_PACKAGE": "src/system/constants/platform-object-names.ts#PLATFORM_OBJECTS_BY_PACKAGE (const)",
     "PLATFORM_OBJECT_PREFIXES": "src/system/constants/platform-object-names.ts#PLATFORM_OBJECT_PREFIXES (const)",
     "PLATFORM_PROVIDED_OBJECT_NAMES": "src/system/constants/platform-object-names.ts#PLATFORM_PROVIDED_OBJECT_NAMES (const)",
@@ -512,6 +515,9 @@
     "Plan": "src/system/license.zod.ts#Plan (type)",
     "PlanParsed": "src/system/license.zod.ts#PlanParsed (type)",
     "PlanSchema": "src/system/license.zod.ts#PlanSchema (const)",
+    "PlatformLocale": "src/system/platform-locales.ts#PlatformLocale (interface)",
+    "PlatformLocaleReadAlias": "src/system/platform-locales.ts#PlatformLocaleReadAlias (type)",
+    "PlatformLocaleTag": "src/system/platform-locales.ts#PlatformLocaleTag (type)",
     "PlatformTranslationBundle": "src/system/translation.zod.ts#PlatformTranslationBundle (type)",
     "PlatformTranslationBundleSchema": "src/system/translation.zod.ts#PlatformTranslationBundleSchema (const)",
     "PlatformTranslationData": "src/system/translation.zod.ts#PlatformTranslationData (type)",
@@ -837,6 +843,7 @@
     "operationMessageTranslationKey": "src/system/operation-message.ts#operationMessageTranslationKey (function)",
     "organizationOwnershipShapeGenerationOf": "src/system/migration.zod.ts#organizationOwnershipShapeGenerationOf (function)",
     "pageTabItemKey": "src/system/i18n-resolver.ts#pageTabItemKey (function)",
+    "platformLocaleTagOf": "src/system/platform-locales.ts#platformLocaleTagOf (function)",
     "preferredLocaleFromHeader": "src/system/i18n-resolver.ts#preferredLocaleFromHeader (function)",
     "renderOperationMessage": "src/system/operation-message.ts#renderOperationMessage (function)",
     "renderValidationMessage": "src/system/validation-message.ts#renderValidationMessage (function)",
 
@@ -126,6 +126,9 @@ export * from './worker.zod';
 export * from './notification.zod';
 export * from './translation.zod';
 export * from './i18n-resolver';
+// The platform locale table (ruling F of #29349): the one list of languages
+// the platform supports, and the read aliases that keep stored codes valid.
+export * from './platform-locales';
 // Localized templates for the built-in field-validation messages (#3957).
 export * from './validation-message';
 // Localized templates for OPERATION-level data refusals (#7307) — a write the
 
@@ -0,0 +1,138 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+//
+// Pins for the platform locale table (ruling F of #29349, phase 1 of #29428,
+// card #30001): the table whole, its read aliases one by one, the
+// case-insensitive lookup and the closed list (no region fallback).
+
+import { describe, it, expect } from 'vitest';
+import {
+  PLATFORM_LOCALES,
+  PLATFORM_LOCALE_TAGS,
+  PLATFORM_LOCALE_READ_ALIASES,
+  platformLocaleTagOf,
+  type PlatformLocaleReadAlias,
+  type PlatformLocaleTag,
+} from './platform-locales';
+import * as SystemBarrel from './index';
+
+describe('PLATFORM_LOCALES: the table, pinned whole', () => {
+  it('holds the eleven languages, in menu order, with their native labels and rtl only on ar', () => {
+    expect(PLATFORM_LOCALES).toEqual([
+      { tag: 'en', label: 'English', rtl: false },
+      { tag: 'zh-Hans', label: '简体中文', rtl: false },
+      { tag: 'zh-Hant', label: '繁體中文', rtl: false },
+      { tag: 'es', label: 'Español', rtl: false },
+      { tag: 'ar', label: 'العربية', rtl: true },
+      { tag: 'fr', label: 'Français', rtl: false },
+      { tag: 'pt-BR', label: 'Português (Brasil)', rtl: false },
+      { tag: 'ru', label: 'Русский', rtl: false },
+      { tag: 'de', label: 'Deutsch', rtl: false },
+      { tag: 'ja', label: '日本語', rtl: false },
+      { tag: 'ko', label: '한국어', rtl: false },
+    ]);
+    expect(PLATFORM_LOCALES.filter((row) => row.rtl).map((row) => row.tag)).toEqual(['ar']);
+  });
+
+  it('PLATFORM_LOCALE_TAGS is the table tags in table order', () => {
+    expect(PLATFORM_LOCALE_TAGS).toEqual(PLATFORM_LOCALES.map((row) => row.tag));
+    expect(new Set(PLATFORM_LOCALE_TAGS).size).toBe(PLATFORM_LOCALE_TAGS.length);
+  });
+
+  it('the table, every row, the tag list and the alias map are frozen', () => {
+    expect(Object.isFrozen(PLATFORM_LOCALES)).toBe(true);
+    for (const row of PLATFORM_LOCALES) expect(Object.isFrozen(row)).toBe(true);
+    expect(Object.isFrozen(PLATFORM_LOCALE_TAGS)).toBe(true);
+    expect(Object.isFrozen(PLATFORM_LOCALE_READ_ALIASES)).toBe(true);
+  });
+
+  it('is exported from the system barrel', () => {
+    expect(SystemBarrel.PLATFORM_LOCALES).toBe(PLATFORM_LOCALES);
+    expect(SystemBarrel.PLATFORM_LOCALE_TAGS).toBe(PLATFORM_LOCALE_TAGS);
+    expect(SystemBarrel.PLATFORM_LOCALE_READ_ALIASES).toBe(PLATFORM_LOCALE_READ_ALIASES);
+    expect(SystemBarrel.platformLocaleTagOf).toBe(platformLocaleTagOf);
+  });
+});
+
+describe('PLATFORM_LOCALE_READ_ALIASES: stored codes keep resolving', () => {
+  const ALIASES: ReadonlyArray<readonly [PlatformLocaleReadAlias, PlatformLocaleTag]> = [
+    ['zh', 'zh-Hans'],
+    ['zh-CN', 'zh-Hans'],
+    ['zh-SG', 'zh-Hans'],
+    ['zh-TW', 'zh-Hant'],
+    ['zh-HK', 'zh-Hant'],
+    ['zh-MO', 'zh-Hant'],
+    ['ja-JP', 'ja'],
+    ['es-ES', 'es'],
+    ['pt', 'pt-BR'],
+    ['en-US', 'en'],
+  ];
+
+  it.each(ALIASES)('%s reads as %s', (code, tag) => {
+    expect(PLATFORM_LOCALE_READ_ALIASES[code]).toBe(tag);
+    expect(platformLocaleTagOf(code)).toBe(tag);
+  });
+
+  it('the map is exactly those ten aliases', () => {
+    expect(PLATFORM_LOCALE_READ_ALIASES).toEqual(Object.fromEntries(ALIASES));
+  });
+
+  it('the map is typed on its ten literal keys: an unlisted code does not index it as defined', () => {
+    const zhCN: 'zh-Hans' = PLATFORM_LOCALE_READ_ALIASES['zh-CN'];
+    expect(zhCN).toBe('zh-Hans');
+    // @ts-expect-error `pt-PT` is not a read alias, so the index is not typed as a table tag.
+    expect(PLATFORM_LOCALE_READ_ALIASES['pt-PT']).toBeUndefined();
+  });
+
+  it('every alias target is a table tag', () => {
+    for (const tag of Object.values(PLATFORM_LOCALE_READ_ALIASES)) {
+      expect(PLATFORM_LOCALE_TAGS).toContain(tag);
+    }
+  });
+
+  it('no alias key is itself a table tag, in any case', () => {
+    const folded = new Set(PLATFORM_LOCALE_TAGS.map((tag) => tag.toLowerCase()));
+    for (const code of Object.keys(PLATFORM_LOCALE_READ_ALIASES)) {
+      expect(folded.has(code.toLowerCase())).toBe(false);
+    }
+  });
+});
+
+describe('platformLocaleTagOf', () => {
+  it.each(PLATFORM_LOCALE_TAGS.map((tag) => [tag]))('the table tag %s answers itself', (tag) => {
+    expect(platformLocaleTagOf(tag)).toBe(tag);
+  });
+
+  // BCP 47 tags are case-insensitive, and stored user locales are not all in
+  // canonical case (#29895 records `zh-cn`).
+  it.each([
+    ['zh-cn', 'zh-Hans'],
+    ['ZH-TW', 'zh-Hant'],
+    ['zh-hans', 'zh-Hans'],
+    ['ZH-HANT', 'zh-Hant'],
+    ['pt-br', 'pt-BR'],
+    ['EN', 'en'],
+    ['en-us', 'en'],
+    ['ja-jp', 'ja'],
+  ])('ignores case: %s reads as %s', (code, tag) => {
+    expect(platformLocaleTagOf(code)).toBe(tag);
+  });
+
+  // The list is closed: no region or script fallback is guessed.
+  it.each(['pt-PT', 'de-AT', 'en-GB', 'zh-Hans-CN', 'es-419', 'fr-CA', 'it', 'he', 'zh-Hant-TW'])(
+    'a code the table and the aliases do not list, %s, answers undefined',
+    (code) => {
+      expect(platformLocaleTagOf(code)).toBeUndefined();
+    },
+  );
+
+  it.each(['zh_CN', ' en', 'en ', 'Chinese', '', 'constructor', 'toString', '__proto__'])(
+    'nothing but case is corrected: %j answers undefined',
+    (code) => {
+      expect(platformLocaleTagOf(code)).toBeUndefined();
+    },
+  );
+
+  it.each([undefined, null, 42, {}, ['en']])('a non-string, %j, answers undefined', (value) => {
+    expect(platformLocaleTagOf(value)).toBeUndefined();
+  });
+});