@@ -0,0 +1,16 @@
+---
+'@objectstack/metadata-protocol': minor
+'@object-ui/app-shell': minor
+---
+
+fix(metadata-protocol): a mapping override is served, a pair's removal of its own override of any overridable type brings the base's item back, and an excluded type's `overrides` refusal names a remedy that works for it (#30062)
+
+Clause-②: no — ADR-0146 D2 says an item in the customization package replaces the base's item and removing it brings the base's back, and ADR-0146's revert ("Restore package original") is deleting the overriding item from `.custom` so the base's document is served again. The 403 on removing a pair's own doc or mapping override, and the unserved mapping override, refused what that text already admits. A removal that names the base still keeps today's answer.
+Metadata-protocol: semantic
+
+- **A mapping override in `<base>.custom` is served.** A mapping item that declares `overrides: { package: '<base>', … }` in the base's customization package now replaces the base's mapping for the by-name read (no `?package`, `?package=<base>`), both lists and the layered read, as page, app, dataset, doc and book already did. The import door (`@objectstack/rest`'s `import-mapping.ts`) resolves a named mapping through that package-less by-name read, so it now gets the pair's mapping.
+- **Removing a pair's own override works for every overridable type.** `DELETE` of a declared override the customization package holds (named with `?package=<base>.custom`) was admitted only for a flow; a doc or mapping override answered `403 NOT_OVERRIDABLE` on the environment kernel. The removal now admits the pair's row for every type `isOverridableMetadataType` names. The row is deleted and the base's item is served again under every address. A removal that names the base (`?package=<base>`) is unchanged: the pair's row stays and its override stays served.
+- **An excluded type's refusal names a remedy that works for it.** A save of `overrides` on a type that takes no override now cites that type's own record (ADR-0146 D6 for the security catalog and code-only types, D1 for a datasource, D9 for a behavioural switch, D10 for a field, ADR-0126 §3 for one-shot types, D2 for the rest) and prescribes a door that exists for that type: a new item under a new name where the type may be created at runtime, the documented switch route for a sharing rule, Setup › Queues for a queue, Setup › Datasources for a datasource, an object extension for a field, and a new version of the base for a type defined only in package source. The error code and status are unchanged.
+- **`@object-ui/app-shell`: the All metadata tile agrees with the Customize door.** On a read-only package, a type's tile reads 可定制 (Customizable) exactly where Studio offers a Customize door for it (flow and app included, whose overlay flag is off) and 只读 (Read-only) elsewhere (doc and mapping, which have no door yet). It no longer reads the overlay flag.
+
+The label precedence of a translated override (card item 3) is not in this change.
@@ -105,7 +105,10 @@ declaring `overrides: { package: 'hotcrm', basedOn: '3.2.0' }` (`basedOn` is the
 `manifest.version` of `hotcrm` it was taken from, recorded and never judged). Only the pair declares an override: an item of any other
 package that depends on `hotcrm` and bears a `hotcrm` item's name is refused at save
 and publish, and its fix is a new name. A permission set, position or capability is
-never overridden; it is copied under a new name. What the reads then serve is in
+never overridden: a permission set or position is copied under a new name, and a
+capability changes only with a new version of the package that declares it. An
+`overrides` on a type that takes none is refused `403 NOT_OVERRIDABLE`, and the
+sentence names that type's own route. What the reads then serve is in
 [Metadata lifecycle](/docs/concepts/metadata-lifecycle#customizing-an-installed-package-the-paired-custom-override-adr-0146).
 `POST /packages/hotcrm/ensure-customization` creates the pair when absent (Studio calls
 it on the first change), and `GET /packages/hotcrm/customizations` lists its overrides,
 
@@ -128,10 +128,15 @@ document **whole** for every read that serves the base's name
   override, `effective` = the override), the list scoped to the base and the
   environment-wide list all serve the override, stamped `_packageId: 'hotcrm'`. The
   declaration counts only from the pair — the stored row's own `package_id` must be
-  `hotcrm.custom` — and today only for a `view`, `dashboard`, `report`, `email_template`,
-  `translation` or `flow`: the rest of `OVERRIDABLE_METADATA_TYPES` (`@objectstack/spec/kernel`)
-  — `page`, `app`, `dataset`, `doc`, `book`, `mapping` and `action` — waits for
-  its doors and is not served yet. A declaration from any other package is ignored.
+  `hotcrm.custom` — and for every type of `OVERRIDABLE_METADATA_TYPES` (`@objectstack/spec/kernel`)
+  but `action`: a `view`, `dashboard`, `report`, `email_template`, `translation`, `flow`,
+  `page`, `app`, `dataset`, `doc`, `book` or `mapping`. An `action` override waits for
+  ADR-0146 D9's conditions and is not served yet. A declaration from any other package is ignored.
+  The import door and the connector pull read a named `mapping` through the by-name read,
+  so they run the pair's mapping.
+- **Removing the override brings the base's back.** `DELETE /meta/:type/:name?package=hotcrm.custom`
+  ("Restore package original") deletes the pair's row, for every type above, and every read
+  then serves the base's document again. A `DELETE` naming `hotcrm` removes nothing of the pair's.
 - **A new locale is not an override.** An `email_template` the pair saves at a locale the
   base does not ship is the pair's own member, served under `hotcrm.custom`, and carries no
   `overrides`; declaring one there is refused (`403 NOT_OVERRIDABLE` at the save, publish
 
@@ -401,12 +401,12 @@ export class ProtocolDiffDeleteLoadFacet {
         // here, but a stored row under its name is, as repair.
         const originGatedRefusal = host.originGatedRemovalRefusal(request.type, request.name);
         // [#28412, ADR-0146 D9 item 1] A removal naming the shipping package's
-        // pair, of a type whose D9 conditions are delivered (`flow` only —
-        // every other open type keeps main's verdict): it removes
-        // the row the override is stored in, and the code package's item is
-        // served — and armed — again. Admitted past the sealed-removal refusal
-        // and told to the store as a runtime-only removal, as the declared
-        // save is ({@link isPairRowRemoval}).
+        // pair, of a type whose declared override the gate admits ([#30062]
+        // every open type, no longer `flow` alone): it removes the row the
+        // override is stored in, and the code package's item is served (a
+        // flow's armed) again. Admitted past the sealed-removal refusal and
+        // told to the store as a runtime-only removal, as the declared save
+        // is ({@link isPairRowRemoval}).
         const pairRowRemoval = isPairRowRemoval(
             request.type, host.packagedArtifactOwner({ type: request.type, name: request.name }), request.packageId,
         );
@@ -755,10 +755,10 @@ export class ProtocolDiffDeleteLoadFacet {
                     // #5927 — was an inline `this.isArtifactBacked(...)` call
                     // with these exact arguments; now reads the method-scoped
                     // binding the receipts share. Same fact, one call fewer.
-                    // [#28412] The pair's row of a type whose D9 conditions
-                    // are delivered (`flow` only, {@link isPairRowRemoval})
+                    // [#28412] The pair's row of a declared override
+                    // ({@link isPairRowRemoval}; [#30062] every open type)
                     // is removed as the declared save wrote it: runtime-only.
-                    // Every other type keeps the intent main gave it.
+                    // Every other removal keeps the intent main gave it.
                     intent: artifactBacked && !pairRowRemoval
                         ? 'override-artifact'
                         : 'runtime-only',
 
@@ -150,8 +150,8 @@ export function declinesStoredRow(
     if (typeof name !== 'string' || name === '') return false;
     if (this.isDeclaredCodeDatasource(type, name)) return true;
     if (!this.isUnservedSealedOverlay(type, name)) return false;
-    // [#29613, ADR-0146 D8 item 2] …except, for a page, app, dataset, doc or
-    // book, the shipping package's declared override: judged as the flow's
+    // [#29613, ADR-0146 D8 item 2] …except, for a page, app, dataset, doc,
+    // book or [#30062] mapping, the shipping package's declared override: judged as the flow's
     // above, on the row's own `package_id` and body, against the package
     // that ships the name. The reads then serve it from its row, as they
     // serve a dashboard's. Every other sealed row of the name stays declined.
 
@@ -15,7 +15,8 @@
 import { describe, expect, it } from 'vitest';
 import { declinesBorrowedEnvelope, servesSealedOverrideRow } from './protocol-package-bindings.js';
 
-const ROW_SERVED = ['page', 'app', 'dataset', 'doc', 'book'] as const;
+/** [#30062] `mapping` the sixth: its reads were measured and its published override was served by none. */
+const ROW_SERVED = ['page', 'app', 'dataset', 'doc', 'book', 'mapping'] as const;
 /** The base's code artifact the hydrator's lookup falls back to for a pair's row. */
 const BASE_ARTIFACT = { _packageId: 'com.example.showcase' };
 
@@ -30,7 +31,7 @@ describe('[#29613] the sealed row-served override types', () => {
         expect(servesSealedOverrideRow('apps')).toBe(true);
     });
 
-    it.each(['mapping', 'action', 'flow', 'object', 'permission', 'view', 'dashboard', 'report', 'email_template'])(
+    it.each(['action', 'flow', 'object', 'permission', 'view', 'dashboard', 'report', 'email_template'])(
         '%s: not a sealed row-served override type',
         (type) => {
             expect(servesSealedOverrideRow(type)).toBe(false);
 
@@ -307,9 +307,9 @@ function boundPackageOf(packageId: unknown): string | undefined {
  * (#22057, `anotherPackageShips`).
  *
  * ⛔ A closed list, judged on the canonical type. [#29613] It includes the
- * five {@link SEALED_ROW_SERVED_OVERRIDE_TYPES} since their reads serve a
- * `.custom` pair's declared override from its row, as these three types'
- * reads do. `flow` registers with no artifact envelope at all (Regime C,
+ * {@link SEALED_ROW_SERVED_OVERRIDE_TYPES} ([#30062] `mapping` the sixth)
+ * since their reads serve a `.custom` pair's declared override from its row,
+ * as these three types' reads do. `flow` registers with no artifact envelope at all (Regime C,
  * #20913), and the boot pull arms its declared override from the bare slot.
  */
 const BORROWED_ENVELOPE_DECLINED_TYPES: ReadonlySet<string> = new Set([
@@ -322,16 +322,19 @@ const BORROWED_ENVELOPE_DECLINED_TYPES: ReadonlySet<string> = new Set([
     'dataset',
     'doc',
     'book',
+    // [#30062] An import mapping's declared override, served from its row as the five above.
+    'mapping',
 ]);
 
 /**
  * [#29613, ADR-0146 D8 item 2] The SEALED types (ADR-0131 D6: a registry
  * entry with `allowEnvironmentOverlay: false`) whose stored row the reads
  * serve when it is the shipping package's declared `.custom` override
- * ({@link isServedOverrideRowOf}): `page`, `app`, `dataset`, `doc` and
- * `book`, the overridable types of ADR-0146 D2 that open no environment
- * overlay. Every other stored row of a name a managed package ships stays
- * unserved for them ({@link isUnservedSealedOverlay}).
+ * ({@link isServedOverrideRowOf}): `page`, `app`, `dataset`, `doc`, `book`
+ * and [#30062] `mapping`, the overridable types of ADR-0146 D2 that open no
+ * environment overlay and wait for no D9 condition. Every other stored row of
+ * a name a managed package ships stays unserved for them
+ * ({@link isUnservedSealedOverlay}).
  *
  * Before, the reads declined the override's row with the rest, and the
  * override was served only from the registry's bare slot, where the hydrator
@@ -340,14 +343,19 @@ const BORROWED_ENVELOPE_DECLINED_TYPES: ReadonlySet<string> = new Set([
  * instead, while the lists answered the override, and the layered read's
  * effective layer and the pair's per-package layer never saw it.
  *
- * ⛔ A closed list, judged on the canonical type. `mapping` is overridable and
- * sealed too, and is not here: no card has measured its reads. `action` and
- * `flow` wait for ADR-0146 D9's conditions (`flow` has its own admission,
+ * [#30062] `mapping` joined once its reads were measured: before, a pair's
+ * mapping override saved and published, and every read (the by-name read the
+ * import door resolves a mapping through, `@objectstack/rest`'s
+ * `import-mapping.ts`, included) answered the base's body, so a published
+ * override did nothing.
+ *
+ * ⛔ A closed list, judged on the canonical type. `action` and `flow` wait for
+ * ADR-0146 D9's conditions (`flow` has its own admission,
  * `declinesStoredRow`'s first branch). Every type here is also in
  * {@link BORROWED_ENVELOPE_DECLINED_TYPES}: the bare entry served no reader
  * the row does not serve now.
  */
-const SEALED_ROW_SERVED_OVERRIDE_TYPES: ReadonlySet<string> = new Set(['page', 'app', 'dataset', 'doc', 'book']);
+const SEALED_ROW_SERVED_OVERRIDE_TYPES: ReadonlySet<string> = new Set(['page', 'app', 'dataset', 'doc', 'book', 'mapping']);
 
 /** [#29613] Whether `type` is one of {@link SEALED_ROW_SERVED_OVERRIDE_TYPES}, folded to the canonical singular. */
 function servesSealedOverrideRow(type: string): boolean {