@@ -0,0 +1,190 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * [#19046] The `object-grid` arm and the view arm must agree on what a PAGE
+ * SIZE is — and must keep disagreeing about whether the bag is closed.
+ *
+ * ## The defect this file closes
+ *
+ * Two arms of this package declared the same authoring member with different
+ * accept sets, and renderers read the looser one:
+ *
+ * | arm | declaration before #19046 | accepted `pageSize: 0`? |
+ * |:--|:--|:--|
+ * | view — `PaginationConfigSchema` (`view.zod.ts`) | `z.number().int().positive().default(25)` | no |
+ * | grid component — `ComponentPropsMap['object-grid']` | `pagination: z.unknown()`, `pageSize: z.number()` | YES, both |
+ *
+ * The view arm pins its refusals BY NAME ('should reject negative pageSize' /
+ * 'should reject zero pageSize', `view.test.ts`), and every other `pageSize`
+ * this package declares is bounded with its own throwing pin
+ * (`kernel/metadata-plugin.zod.ts`, `marketplace/marketplace.zod.ts`) — so the
+ * component arm was the outlier, not the norm. It was not theoretical:
+ * objectui#9853 measured an authored `pagination.pageSize: 0` reaching
+ * `ObjectGrid`, going out on the wire as `$top: 0` and rendering ZERO ROWS,
+ * through this arm. objectui#9896 repaired the consumer half; this is the
+ * declaration half.
+ *
+ * ## The two halves of this pin, and why the second one is not optional
+ *
+ * 1. **The page-size accept sets are now one set.** §1 and §2 assert the
+ *    refusals by name on the component arm, each beside a LIT CONTROL that a
+ *    legal value still parses — a refusal pin with no lit control passes just
+ *    as well when the door has stopped accepting anything at all.
+ * 2. **The bag is still OPEN.** §3 asserts a sibling key inside `pagination`
+ *    still parses and survives byte-identically. The honest fix for §1 is a
+ *    bound on two members; closing the bag would refuse every sibling key this
+ *    door has accepted since it was written — the `…` in its own describe says
+ *    authors write them — which is a WIDER narrowing than the measured defect
+ *    and a different decision. Without §3 that widening lands silently, since
+ *    every §1 assertion passes under it too.
+ *
+ * §4 states the cross-arm agreement and the cross-arm asymmetry as one table:
+ * on a page-size VALUE the two arms answer identically; on an unknown KEY they
+ * deliberately answer differently (`PaginationConfigSchema` is a `strictObject`
+ * — `view-union-retirement-prescription.test.ts` §3 pins its `unrecognized_keys`
+ * — and the component bag is a `z.looseObject`). A future author harmonising
+ * the two arms 'for consistency' reds §3 and §4 rather than discovering the
+ * consequence in a renderer.
+ */
+
+import { describe, it, expect } from 'vitest';
+import type { z } from 'zod';
+
+import { ComponentPropsMap } from './component.zod';
+import { PaginationConfigSchema } from './view.zod';
+
+const grid = () => ComponentPropsMap['object-grid'];
+
+/** The issue codes and paths a refusal carries, so a refusal for the WRONG reason reds. */
+function issues(result: z.ZodSafeParseResult<unknown>): { code: string; path: string }[] {
+  if (result.success) return [];
+  return result.error.issues.map((i) => ({ code: i.code, path: i.path.join('.') }));
+}
+
+/** Every value that is not a page size, with the issue code each one must raise. */
+const NOT_A_PAGE_SIZE: ReadonlyArray<readonly [label: string, value: unknown, code: string]> = [
+  ['zero', 0, 'too_small'],
+  ['negative', -10, 'too_small'],
+  ['non-integer', 25.5, 'invalid_type'],
+];
+
+// ───────────────────────────────────────────────────────────────────────────
+// §1 `pagination.pageSize` — the member the measured defect came through.
+// ───────────────────────────────────────────────────────────────────────────
+
+describe('§1 object-grid `pagination.pageSize` refuses what the view arm refuses', () => {
+  it('should reject zero pageSize', () => {
+    const r = grid().safeParse({ pagination: { pageSize: 0 } });
+    expect(r.success).toBe(false);
+    expect(issues(r)).toContainEqual({ code: 'too_small', path: 'pagination.pageSize' });
+  });
+
+  it('should reject negative pageSize', () => {
+    const r = grid().safeParse({ pagination: { pageSize: -10 } });
+    expect(r.success).toBe(false);
+    expect(issues(r)).toContainEqual({ code: 'too_small', path: 'pagination.pageSize' });
+  });
+
+  it('should reject non-integer pageSize', () => {
+    const r = grid().safeParse({ pagination: { pageSize: 25.5 } });
+    expect(r.success).toBe(false);
+    expect(issues(r)).toContainEqual({ code: 'invalid_type', path: 'pagination.pageSize' });
+  });
+
+  it('LIT CONTROL — a legal pageSize still parses and is preserved', () => {
+    const r = grid().safeParse({ objectName: 'showcase_task', pagination: { pageSize: 50 } });
+    expect(issues(r)).toEqual([]);
+    expect(r.success && r.data.pagination).toStrictEqual({ pageSize: 50 });
+  });
+
+  it('should reject zero values in pageSizeOptions', () => {
+    const r = grid().safeParse({ pagination: { pageSize: 25, pageSizeOptions: [10, 0, 50] } });
+    expect(r.success).toBe(false);
+    expect(issues(r)).toContainEqual({ code: 'too_small', path: 'pagination.pageSizeOptions.1' });
+  });
+
+  it('should reject negative values in pageSizeOptions', () => {
+    const r = grid().safeParse({ pagination: { pageSize: 25, pageSizeOptions: [10, -25, 50] } });
+    expect(r.success).toBe(false);
+    expect(issues(r)).toContainEqual({ code: 'too_small', path: 'pagination.pageSizeOptions.1' });
+  });
+
+  it('LIT CONTROL — the whole ruled bag parses, options included', () => {
+    const bag = { pageSize: 50, pageSizeOptions: [25, 50, 100] };
+    const r = grid().safeParse({ pagination: bag });
+    expect(issues(r)).toEqual([]);
+    expect(r.success && r.data.pagination).toStrictEqual(bag);
+  });
+});
+
+// ───────────────────────────────────────────────────────────────────────────
+// §2 the FLAT shorthand — the second door onto the same renderer read.
+// ───────────────────────────────────────────────────────────────────────────
+
+describe('§2 object-grid flat `pageSize` shorthand carries the same accept set', () => {
+  for (const [label, value, code] of NOT_A_PAGE_SIZE) {
+    it(`should reject ${label} pageSize on the flat shorthand`, () => {
+      const r = grid().safeParse({ pageSize: value });
+      expect(r.success).toBe(false);
+      expect(issues(r)).toContainEqual({ code, path: 'pageSize' });
+    });
+  }
+
+  it('LIT CONTROL — the flat shorthand still parses and keeps its value', () => {
+    const r = grid().safeParse({ objectName: 'showcase_task', pageSize: 25, showPagination: true });
+    expect(issues(r)).toEqual([]);
+    expect(r.success && r.data.pageSize).toBe(25);
+  });
+});
+
+// ───────────────────────────────────────────────────────────────────────────
+// §3 THE OPENNESS PIN — what #19046 deliberately did NOT narrow.
+// ───────────────────────────────────────────────────────────────────────────
+
+describe('§3 the `pagination` bag stays open — the narrowing did not reach sibling keys', () => {
+  it('a sibling key inside the bag parses, with no `unrecognized_keys` issue', () => {
+    const bag = { pageSize: 25, position: 'bottom' };
+    const r = grid().safeParse({ pagination: bag });
+    expect(issues(r)).toEqual([]);
+    expect(r.success).toBe(true);
+  });
+
+  it('and it survives the parse byte-identically — passed through, not stripped', () => {
+    const bag = { pageSize: 25, position: 'bottom', mode: { server: true } };
+    const r = grid().safeParse({ pagination: bag });
+    expect(r.success && r.data.pagination).toStrictEqual(bag);
+  });
+
+  it('a bag carrying ONLY sibling keys parses — no page-size member is required', () => {
+    const bag = { position: 'bottom' };
+    const r = grid().safeParse({ pagination: bag });
+    expect(issues(r)).toEqual([]);
+    expect(r.success && r.data.pagination).toStrictEqual(bag);
+  });
+});
+
+// ───────────────────────────────────────────────────────────────────────────
+// §4 CROSS-ARM — one accept set for the VALUE, two verdicts for a KEY.
+// ───────────────────────────────────────────────────────────────────────────
+
+describe('§4 the two arms agree on a page size and disagree on openness, both on purpose', () => {
+  for (const [label, value] of NOT_A_PAGE_SIZE) {
+    it(`both arms refuse a ${label} pageSize — the disagreement #19046 closes`, () => {
+      expect(PaginationConfigSchema.safeParse({ pageSize: value }).success, 'view arm').toBe(false);
+      expect(grid().safeParse({ pagination: { pageSize: value } }).success, 'component arm').toBe(false);
+    });
+  }
+
+  it('LIT CONTROL — both arms accept the same legal page size', () => {
+    expect(PaginationConfigSchema.safeParse({ pageSize: 50 }).success, 'view arm').toBe(true);
+    expect(grid().safeParse({ pagination: { pageSize: 50 } }).success, 'component arm').toBe(true);
+  });
+
+  it('an unknown KEY is refused by the view arm and accepted by the component bag', () => {
+    const bag = { pageSize: 25, position: 'bottom' };
+    const view = PaginationConfigSchema.safeParse(bag);
+    expect(view.success, 'the view arm is a strictObject and stays closed').toBe(false);
+    expect(issues(view).map((i) => i.code)).toContain('unrecognized_keys');
+    expect(grid().safeParse({ pagination: bag }).success, 'the component bag stays open').toBe(true);
+  });
+});
@@ -2501,6 +2501,21 @@ const objectBlockHistory = (type: string) =>
  */
 const FILTERS_TO_FILTER = { filters: 'filter' } as const;
 
+/**
+ * A page size — a positive integer, and nothing else.
+ *
+ * ONE spelling for a rule the rest of this package already carries, so the
+ * component arm cannot drift from it again: `PaginationConfigSchema`
+ * (`view.zod.ts`) declares `pageSize: z.number().int().positive()` and
+ * `pageSizeOptions: z.array(z.number().int().positive())`; `MetadataQuery`
+ * (`kernel/metadata-plugin.zod.ts`) and the two marketplace request schemas
+ * (`marketplace/marketplace.zod.ts`) say `z.number().int().min(1)`. Each of
+ * those pins its own refusal of `0` by name. Until #19046 the `object-grid`
+ * door below said `z.number()` and `z.unknown()`, and was the only
+ * page-size declaration in the package that accepted `0`.
+ */
+const GridPageSizeSchema = z.number().int().positive();
+
 /**
  * `object-grid` (objectui `plugin-grid/src/ObjectGrid.tsx` @ `eb7f586b`).
  * Read points per key: `objectName` (throughout), `columns`/`fields` (:714-715),
@@ -2629,9 +2644,53 @@ export const ObjectGridPropsSchema = lazySchema(() => strictObject({
     + 'becomes `sort: [{ field, order }]`); the pair itself is unchanged. '
     + 'Run `os migrate meta --from 17` to list the mechanical edits for existing sources; apply them by hand.',
   ),
-  pagination: z.unknown().optional()
-    .describe('Pagination config ({ pageSize, pageSizeOptions, … }); its presence enables paging'),
-  pageSize: z.number().optional().describe('Flat page-size shorthand; `pagination.pageSize` wins when both are set'),
+  /**
+   * Pagination config — the two members whose value is a PAGE SIZE bounded to
+   * {@link GridPageSizeSchema}, the accept set the view arm has ruled all
+   * along, and the bag itself left OPEN.
+   *
+   * The `z.unknown()` this door carried until #19046 was a read-point record
+   * of the same #7751 vintage as its `filter` and `sort` neighbours above, and
+   * it made the SAME authored member carry two accept sets, of which renderers
+   * read the looser: `PaginationConfigSchema` refuses `pageSize: 0` and pins
+   * that refusal by name ('should reject zero pageSize' / 'should reject zero
+   * values in pageSizeOptions', `view.test.ts`), while this door receipted it
+   * `success: true`. Measured at objectui#9853: an authored
+   * `pagination.pageSize: 0` reached `ObjectGrid`, went out on the wire as
+   * `$top: 0` and rendered ZERO ROWS, with no grouping needed to trigger it,
+   * and it reached the renderer through THIS arm — the view arm would have
+   * refused it. objectui#9896 repaired the consumer half (a resolver at every
+   * read point); this is the declaration half.
+   *
+   * **`z.looseObject`, not `strictObject` — the bag stays open, deliberately.**
+   * `PaginationConfigSchema` is itself closed, but reusing it here would
+   * refuse every sibling key this door has accepted since it was written — the
+   * `…` in its own describe says authors pass them — which is a wider
+   * narrowing than the defect measured above and a different decision. So what
+   * narrows is the accept set of a page size; what does NOT narrow is which
+   * keys the bag may carry. `BuildProgressFrameSchema`
+   * (`ai/build-progress.zod.ts`) is the house precedent for a floor-not-ceiling
+   * shape, and `DashboardWidgetConfigSchema` for an open bag with declared
+   * members.
+   *
+   * Read points measured at objectui `d18322415`: `ObjectGrid.tsx:1209` and
+   * `:1628` read `(schema.pagination as any)?.pageSize ?? schema.pageSize`,
+   * `:4179` reads `schema.pagination?.pageSize` and `:4359`
+   * `schema.pagination?.pageSizeOptions` — those two are the only members any
+   * read point on this door names, and the objectui registry has published
+   * this input as `type: 'object'` all along (`plugin-grid/src/index.tsx:223`),
+   * so a non-object value here was already answered `type-mismatch` one tier
+   * down while this schema accepted it. `:4175` reads presence only
+   * (`schema.pagination !== undefined ? true : …`), which is why an authored
+   * `pagination: false` used to mean paging ON.
+   */
+  pagination: z.looseObject({
+    pageSize: GridPageSizeSchema.optional(),
+    pageSizeOptions: z.array(GridPageSizeSchema).optional(),
+  }).optional()
+    .describe('Pagination config ({ pageSize, pageSizeOptions, … }); its presence enables paging. `pageSize` and every `pageSizeOptions` entry is a positive integer — the accept set the view arm\'s `PaginationConfigSchema` already rules; the bag stays open, so other keys pass through unvalidated'),
+  pageSize: GridPageSizeSchema.optional()
+    .describe('Flat page-size shorthand, a positive integer; `pagination.pageSize` wins when both are set'),
   showPagination: z.boolean().optional().describe('Show the pager (read only when `pagination` is absent)'),
   searchableFields: z.array(z.string()).optional()
     .describe('Fields the toolbar search queries; a non-empty list enables search'),