diff --git a/.changeset/26128-translation-item-snake-case-name.md b/.changeset/26128-translation-item-snake-case-name.md
new file mode 100644
index 00000000000..c0b41cc1934
--- /dev/null
+++ b/.changeset/26128-translation-item-snake-case-name.md
@@ -0,0 +1,13 @@
+---
+'@objectstack/spec': patch
+'@objectstack/core': patch
+---
+
+fix(spec): `TranslationItemSchema.name` no longer tells authors to name a translation item after its locale tag
+
+Clause-②: no
+Metadata-protocol: none
+
+The `name` describe said a translation item was "conventionally the locale code (`zh-CN`)", but the metadata save door's item-name grammar refuses `zh-CN` (uppercase and a hyphen), so an author or agent following the describe got a 400 `INVALID_REQUEST` on the first save. The describe now says a translation item is named in snake_case like every metadata item (e.g. `zh_cn`), with the BCP-47 tag in `locale`. The save door and the runtime sync's read-side name fallback for rows stored before `locale` became required are unchanged; the sync's skip warning now points authors at `locale` only.
+
+`@objectstack/core`: the authored-translation sync's no-locale skip warning now tells authors to set `locale` to the item's BCP-47 tag (e.g. `zh-CN`), instead of suggesting they name the item after it.
diff --git a/content/docs/references/system/translation.mdx b/content/docs/references/system/translation.mdx
index a28db115d72..d45e85fcdc5 100644
--- a/content/docs/references/system/translation.mdx
+++ b/content/docs/references/system/translation.mdx
@@ -742,7 +742,7 @@ One locale of translations — the `translation` metadata type
 | **metadataForms** | `Record<string, { label?: string; description?: string; sections?: Record<string, object>; fields?: Record<string, object> }>` | optional | Translations for metadata-type configuration forms keyed by metadata type |
 | **settingsCommon** | `{ sourceLabels?: object }` | optional | Cross-namespace Settings UI strings |
 | **locale** | `string` | ✅ | BCP-47 locale this item translates (e.g. "zh-CN") |
-| **name** | `string` | optional | Item name — conventionally the locale code (`zh-CN`); the runtime sync falls back to it when `locale` is absent |
+| **name** | `string` | optional | Item name — snake_case like every metadata item (e.g. `zh_cn`); the BCP-47 tag goes in `locale` |
 | **label** | `string` | optional | Human-readable label shown in metadata lists |
 | **_lock** | `Enum<'none' \| 'no-overlay' \| 'no-delete' \| 'full'>` | optional | Item-level lock — controls overlay & delete (ADR-0010). |
 | **_lockReason** | `string` | optional | Human-readable reason shown when a write is refused by _lock. |
diff --git a/packages/core/src/fallbacks/authored-translation-sync.ts b/packages/core/src/fallbacks/authored-translation-sync.ts
index 05e37c6b9a3..b116f4ceddc 100644
--- a/packages/core/src/fallbacks/authored-translation-sync.ts
+++ b/packages/core/src/fallbacks/authored-translation-sync.ts
@@ -192,7 +192,7 @@ export async function readAuthoredTranslationLayer(
     if (!locale) {
       logger?.warn?.(
         `[i18n] authored translation '${row?.name}' has no resolvable locale `
-        + "(set the top-level 'locale', or name the item after its BCP-47 locale) — skipped",
+        + "(set the top-level 'locale' to its BCP-47 tag, e.g. 'zh-CN') — skipped",
       );
       continue;
     }
diff --git a/packages/metadata-protocol/src/protocol.item-name-grammar.test.ts b/packages/metadata-protocol/src/protocol.item-name-grammar.test.ts
index 3e98e36290e..03b8f897ce3 100644
--- a/packages/metadata-protocol/src/protocol.item-name-grammar.test.ts
+++ b/packages/metadata-protocol/src/protocol.item-name-grammar.test.ts
@@ -300,3 +300,27 @@ describe('#12194 — the refusal is scoped to the doors that MINT or PROMOTE', (
         ).rejects.toMatchObject({ code: 'INVALID_REQUEST', status: 400 });
     });
 });
+
+describe('#26128 — a translation item is named in snake_case, the BCP-47 tag goes in `locale`', () => {
+    // `TranslationItemSchema.name` once called the locale tag (`zh-CN`) the
+    // conventional item name, while this door refused it. The describe moved;
+    // the door did not. Both halves are pinned here so they cannot drift again.
+    const TRANSLATION_BODY = { locale: 'zh-CN', label: '简体中文' };
+
+    it('refuses a tag-shaped item name (`zh-CN`) with the grammar refusal and persists nothing', async () => {
+        const { protocol, rows } = makeProtocol();
+        await expect(
+            protocol.saveMetaItem({ type: 'translation', name: 'zh-CN', item: { ...TRANSLATION_BODY, name: 'zh-CN' } }),
+        ).rejects.toMatchObject({ code: 'INVALID_REQUEST', status: 400, message: expect.stringMatching(GRAMMAR_MESSAGE) });
+        expect(metaRows(rows)).toHaveLength(0);
+    });
+
+    it('accepts the snake_case name (`zh_cn`) with `locale: \'zh-CN\'`', async () => {
+        const { protocol, rows } = makeProtocol();
+        const result = await protocol.saveMetaItem({ type: 'translation', name: 'zh_cn', item: { ...TRANSLATION_BODY, name: 'zh_cn' } });
+        expect(result.success).toBe(true);
+        expect(metaRows(rows)).toHaveLength(1);
+        expect(metaRows(rows)[0]!.name).toBe('zh_cn');
+        expect(JSON.parse(metaRows(rows)[0]!.metadata).locale).toBe('zh-CN');
+    });
+});
diff --git a/packages/objectql/src/protocol-publish-canonical-fold.test.ts b/packages/objectql/src/protocol-publish-canonical-fold.test.ts
index d0ea71a2e9b..0a14d0f3c0a 100644
--- a/packages/objectql/src/protocol-publish-canonical-fold.test.ts
+++ b/packages/objectql/src/protocol-publish-canonical-fold.test.ts
@@ -265,8 +265,8 @@ async function refusalOf(fn: () => Promise<unknown>): Promise<{ code?: string; s
 
 /**
  * A `translation` body. `TranslationItemSchema` requires `locale`; `name` is
- * declared and optional, and is deliberately NOT snake_case-constrained for
- * this type (translation items are conventionally named after their locale).
+ * declared and optional; like every metadata item it is named in snake_case
+ * (`zh_cn`), with the BCP-47 tag in `locale`.
  */
 const translationBody = (label: string) => ({ locale: 'zh-CN', name: 'zh_cn', label });
 
diff --git a/packages/spec/src/system/translation.zod.ts b/packages/spec/src/system/translation.zod.ts
index d8bd010ad95..39bb0800ca0 100644
--- a/packages/spec/src/system/translation.zod.ts
+++ b/packages/spec/src/system/translation.zod.ts
@@ -2255,12 +2255,15 @@ export const TranslationItemSchema = lazySchema(() => strictObject({
   // Undeclared, they were stripped on every parse, so the metadata door quietly
   // discarded an item's own name on the way through.
   //
-  // Not snake_case-constrained the way `job.name` is: translation items are
-  // conventionally named after their locale (`zh-CN`), and the runtime sync
-  // reads `row.name` as a locale fallback for exactly that reason. Optional
-  // because `locale`, not `name`, is this type's required identity — that call
-  // was deliberate (a skipped item is invisible) and is not being reopened.
-  name: z.string().optional().describe('Item name — conventionally the locale code (`zh-CN`); the runtime sync falls back to it when `locale` is absent'),
+  // Named like every other metadata item: snake_case (`zh_cn`), with the BCP-47
+  // tag in `locale`. The save door's item-name grammar
+  // (`METADATA_ITEM_NAME_PATTERN`) refuses a tag-shaped name such as `zh-CN`,
+  // so this shape does not re-check it. The runtime sync still reads a
+  // tag-shaped `row.name` as a locale fallback, but only for rows stored before
+  // `locale` became required. Optional because `locale`, not `name`, is this
+  // type's required identity — that call was deliberate (a skipped item is
+  // invisible) and is not being reopened.
+  name: z.string().optional().describe('Item name — snake_case like every metadata item (e.g. `zh_cn`); the BCP-47 tag goes in `locale`'),
   label: z.string().optional().describe('Human-readable label shown in metadata lists'),
 
   // ADR-0010 — runtime protection envelope (internal — set by the loader).