@@ -0,0 +1,20 @@
+---
+'@objectstack/lint': minor
+---
+
+fix(lint)!: a stored page sort naming a field its object lacks is refused by `os validate` and at the page publish door (`page-field-unknown`, error), on every page sort slot (#30093)
+
+Clause-②: no (narrowing) — an unknown sort field on a page slot moves from silent or warning to error: `os validate` / `os build` / `os lint` and the `page` publish door refuse a page sort they accepted before.
+Metadata-protocol: narrowed
+Skills-docs: updated here — content/docs/deployment/validating-metadata.mdx
+
+<!-- adr-0087: not-required (no-migration-prescription) No key of any schema is added, removed or renamed: every page sort slot keeps its shape and meaning, and the build and the page publish door now give an unknown field there the verdict a list view sort already gets. A refused name never sorted anything (the list door answered every read 400 INVALID_SORT), so there is no rewrite that keeps what the author meant; the author names a real field, and the refusal says which. -->
+
+**BREAKING** accept-set narrowing at the page publish door (`PUT /api/v1/meta/page/NAME`; Studio, REST and MCP authors) and in `os validate` / `os build` / `os lint`.
+
+- **Before.** A page sort naming a field the object does not have saved green, and its first read, and every read after it, answered `400 INVALID_SORT` at the list door. A list page's `interfaceConfig.sort` and a `record:related_list` block's `sort` drew a `page-field-unknown` warning on the CLI alone; an element `dataSource.sort`, a related list's `parentDataSource.sort`, an app page's `record.sort` and the own `sort` of a `record:line_items`, `list-view` or `object-*` block were read by nothing.
+- **Now.** Every one of those slots is judged by `validateSortableFields`, the reference-integrity member the page publish door already runs, and an unknown name is `page-field-unknown` at `error`, at the slot's path, bound to the object the slot's renderer reads (`dataSource.object`, else the block's object prop; `interfaceConfig.source`, else the page's `object`; `parentDataSource.object`; `record.object`). The page door refuses it `422 INVALID_METADATA`. A registry-injected column on an `external` object is `page-field-unprovisioned` at `warning`, as before. `validatePageFieldBindings` no longer reads a page sort, so each slot has one reader.
+- **Not judged.** A dotted relationship path (the list door refuses it as its own verdict), a system column such as `created_at`, an object the stack (or the publish snapshot) does not carry, and an object with no field map.
+- **Not changed.** A stored page already carrying such a sort keeps loading; only its next save is judged, and its read answers 400 as it did before.
+
+**What an author does.** Name a field the object declares, or add the field to the object. A refused name never sorted the page, so there is nothing to keep.
@@ -163,12 +163,20 @@ component silently skips it and the page renders one item short.
 
 Which object a component binds follows `dataSource.object` → `properties.object`
 → the page's `object`, so a multi-object page is checked per element rather than
-against one page-wide guess. A `record:related_list`'s `columns`/`sort`/`filter`
+against one page-wide guess. A `record:related_list`'s `columns`/`filter`
 resolve against its **related** object (`objectName`), and its add-picker against
 its own. Advisory, like form-layout field references — every consumer degrades
 rather than failing. The same descriptor table drives the react page surface
 (§10), so a component is described once and checked wherever it is authored.
 
+A page **sort** is the exception, because no consumer degrades it: the list door
+answers an unknown sort field `400 INVALID_SORT` on every load. So every stored
+page sort (an element's `dataSource.sort`, a related list's `sort` and
+`parentDataSource.sort`, a list block's own `sort`, `interfaceConfig.sort`, an app
+page's `record.sort`) naming a field the bound object lacks is a
+`page-field-unknown` **error**, and the page publish door refuses the save with
+`422 INVALID_METADATA`.
+
 Skipped, to keep false positives at zero: relationship paths (`account.name`,
 resolved by the query engine), registry-injected system fields (`created_at`,
 `owner_id`, …), components bound to an object another package defines, and
 
@@ -1252,8 +1252,9 @@ export const AUTHORING_RULES: readonly AuthoringRule[] = [
     // [#30023] `page` joins, NARROW by the same mechanism: a page write reaches
     // exactly `validateSortableFields`, the one member that declares `page`,
     // so a stored page sort naming a field the list door refuses
-    // (`sortable: false`, a `formula`) is refused at publish rather than at
-    // its first fetch. Every other member keeps its declaration.
+    // (`sortable: false`, a `formula`, and since #30093 a field the object
+    // does not have, as `page-field-unknown`) is refused at publish rather
+    // than at its first fetch. Every other member keeps its declaration.
     surfaces: CLI_AND_RUNTIME,
     runtimeTypes: ['flow', 'view', 'object', 'dataset', 'report', 'page'],
     run: (stack, ctx) => validateReferenceIntegrity(stack, ctx),
 
@@ -286,7 +286,11 @@ export const REFERENCE_INTEGRITY_RULES: readonly ReferenceIntegrityRule[] = [
   // [#30023] `page` joins: since the projection's `author-declared` verdict
   // the member also walks every stored PAGE sort (element `dataSource.sort`, a
   // block's own `sort`, `interfaceConfig.sort`, `record.sort`) and judges it
-  // by the sortability projection alone. It resolves only against
+  // by the sortability projection. [#30093] It also asks each page sort
+  // existence (`page-field-unknown`, `error`) and provenance
+  // (`page-field-unprovisioned`, `warning`), which `validatePageFieldBindings`
+  // no longer reads, so the page door refuses an unknown page sort field too.
+  // It resolves only against
   // `stack.objects`, which the per-write page snapshot carries, so it has no
   // missing-collection false-positive channel — the #9313 reason, one write
   // type over. It is the only member that declares `page`, so a page write
 
@@ -423,7 +423,10 @@ describe('validatePageFieldBindings — a related list splits its child and pare
     ]]);
   });
 
-  it('a dataSource-bound list checks sort, filter and relationshipField against the child too', () => {
+  // [#30093] The list's `sort` is a stored page sort, judged by
+  // `validateSortableFields` at the list door's grade
+  // (`validate-sortable-fields.test.ts` pins every slot), so it is not read here.
+  it('a dataSource-bound list checks filter and relationshipField against the child too, and leaves sort to the sort rule', () => {
     expect(findingsOf({
       dataSource: { object: 'crm_account' },
       properties: {
@@ -432,7 +435,6 @@ describe('validatePageFieldBindings — a related list splits its child and pare
         filter: [{ field: 'ghost_filter', operator: 'equals', value: 'x' }],
       },
     }).map(([, , path, message]) => [path, message])).toEqual([
-      [`${LIST}.sort[0].field`, expect.stringContaining('"ghost_sort" is not a field on object "crm_account"')],
       [`${LIST}.filter[0].field`, expect.stringContaining('"ghost_filter" is not a field on object "crm_account"')],
       [`${LIST}.relationshipField`, expect.stringContaining('"ghost_fk" is not a field on object "crm_account"')],
     ]);
@@ -731,30 +733,27 @@ describe('validatePageFieldBindings — false-positive floor', () => {
   });
 });
 
-describe('validatePageFieldBindings — legacy bare-string sort (#4340)', () => {
-  /**
-   * `ListViewSchema.sort` still accepts `"created_at desc"`. Reading the whole
-   * string as a field name reported `"amount desc"` as unknown — a finding
-   * whose "field" the author never wrote, and one no fix could satisfy. The
-   * shared `sortFieldRefs` reads its head instead, the way the renderer does.
-   */
-  it('judges the head segment, not the whole "field desc" string', () => {
+// [#30093] A list page's `interfaceConfig.sort` is a stored page sort, judged
+// by `validateSortableFields` (existence at `error`, the legacy string form read
+// by its head — the #4340 reading, pinned there), so this walk reads none of it.
+describe('validatePageFieldBindings — a stored page sort is not read here (#30093)', () => {
+  it('reports nothing for an unknown interfaceConfig.sort, in either form, and still reads the columns', () => {
     const listPage = (sort: unknown) => ({
       ...baseStack(),
       pages: [
         {
           name: 'list_page',
           type: 'list',
           object: 'crm_lead',
-          interfaceConfig: { source: 'crm_lead', columns: ['name'], sort },
+          interfaceConfig: { source: 'crm_lead', columns: ['name', 'ghost_col'], sort },
         },
       ],
     });
-    expect(validatePageFieldBindings(listPage('amount desc'))).toEqual([]);
-    const bad = validatePageFieldBindings(listPage('ghost_col desc'));
-    expect(bad).toHaveLength(1);
-    expect(bad[0].message).toContain('"ghost_col"');
-    expect(bad[0].message).not.toContain('ghost_col desc');
+    for (const sort of ['ghost_sort desc', [{ field: 'ghost_sort', order: 'desc' }]]) {
+      expect(validatePageFieldBindings(listPage(sort)).map((f) => f.path)).toEqual([
+        'pages[0].interfaceConfig.columns[1]',
+      ]);
+    }
   });
 });
 
 
@@ -52,6 +52,21 @@
  * same skips, same rule id: the two surfaces agree on what counts as a field by
  * construction rather than by two lists that happen to match, which is the
  * drift #4330 had just finished removing from the system-field lists.
+ *
+ * ── Stored page sorts are not read here (#30093) ─────────────────────────
+ *
+ * A page `sort` is not a binding a renderer skips: it lowers into the list
+ * door's ORDER BY, which answers an unknown name `400 INVALID_SORT` on the
+ * first load and every load after it. So every page sort slot (a component's
+ * `dataSource.sort`, a related list's `sort` and `parentDataSource.sort`, each
+ * sort-carrying block's own `sort`, `interfaceConfig.sort`, an app page's
+ * `record.sort`) is judged by `validateSortableFields`, under this family's
+ * ids: `page-field-unknown` at `error`, `page-field-unprovisioned` at
+ * `warning`. That member is the one the page publish door runs, so the miss
+ * refuses the save instead of publishing a page that breaks on its first read.
+ * Until #30093 this walk read two of those slots at `warning` and the rest
+ * were read by nothing. The react surface's sort props are not page metadata
+ * slots and keep their own reading in `validate-react-page-props`.
  */
 
 export const PAGE_FIELD_UNKNOWN = 'page-field-unknown';
@@ -600,6 +615,20 @@ export function checkFieldRefs(
   return findings;
 }
 
+/**
+ * [#30093] Is `ref` one a related list's `sort` prop yielded? A STORED page
+ * sort lowers into the list door's ORDER BY, which answers an unknown name
+ * `400 INVALID_SORT` on every load, so it is not the `skipped` miss this pass
+ * grades: `validateSortableFields` asks every page sort slot existence,
+ * provenance and sortability, under this family's ids, and it is the member the
+ * page publish door runs. {@link relatedListFieldRefs} keeps yielding the
+ * sort refs for its out-of-repo callers; only this walk sets them aside.
+ */
+function isPageSortRef(ref: FieldRef, propsPath: string): boolean {
+  const sortPath = `${propsPath}.sort`;
+  return ref.path === sortPath || ref.path.startsWith(`${sortPath}[`) || ref.path.startsWith(`${sortPath}.`);
+}
+
 export function validatePageFieldBindings(stack: AnyRec): PageFieldFinding[] {
   const findings: PageFieldFinding[] = [];
   if (!stack || typeof stack !== 'object') return findings;
@@ -646,7 +675,14 @@ export function validatePageFieldBindings(stack: AnyRec): PageFieldFinding[] {
         // parent; without it, `properties.objectName` names the child.
         const split = relatedListFieldRefs(props, base);
         const dataSource = isRec(component.dataSource) ? component.dataSource : undefined;
-        checkRefs(split.related, strName(dataSource?.object) ?? split.relatedObject, where);
+        // [#30093] The list's `sort` is a stored page sort, judged by
+        // `validateSortableFields` at the list door's grade (see
+        // {@link isPageSortRef}); every other child-side ref stays here.
+        checkRefs(
+          split.related.filter((ref) => !isPageSortRef(ref, base)),
+          strName(dataSource?.object) ?? split.relatedObject,
+          where,
+        );
         // `relationshipValueField` names a field on the PARENT — the record the
         // list hangs off, never its own child `dataSource`. The parent is the
         // list's own `parentDataSource.object` when it declares one (ruling B on
@@ -693,9 +729,10 @@ export function validatePageFieldBindings(stack: AnyRec): PageFieldFinding[] {
     if (cfg) {
       const cfgObject = strName(cfg.source) ?? strName(page.object);
       const base = `pages[${pi}].interfaceConfig`;
+      // [#30093] `cfg.sort` is a stored page sort: `validateSortableFields`
+      // judges it, at the list door's grade.
       const refs: FieldRef[] = [
         ...fieldRefsFrom(cfg.columns, `${base}.columns`),
-        ...sortFieldRefs(cfg.sort, `${base}.sort`),
         ...filterFieldRefs(cfg.filterBy, `${base}.filterBy`),
       ];
       const userFilters = isRec(cfg.userFilters) ? cfg.userFilters : undefined;