diff --git a/examples/app-showcase/src/data/objects/cascading-select.object.ts b/examples/app-showcase/src/data/objects/cascading-select.object.ts
new file mode 100644
index 0000000000..ba0f66f5ff
--- /dev/null
+++ b/examples/app-showcase/src/data/objects/cascading-select.object.ts
@@ -0,0 +1,89 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+import { ObjectSchema, Field } from '@objectstack/spec/data';
+import { P } from '@objectstack/spec';
+
+/**
+ * Cascading Select — the B3 (#1583) dynamic-field-options runtime fixture.
+ *
+ * Demonstrates per-option `SelectOption.visibleWhen` end to end, through the
+ * SERVED pipeline (defineStack → REST metadata → form renderer + the objectql
+ * write path), with the dual-side guarantee B3 is built on: the client narrows
+ * the offered set for UX, but the SERVER is the boundary.
+ *
+ *  - `country` → `province` CASCADE. `province` declares `dependsOn: ['country']`
+ *    (so the form gates it until a country is chosen and re-filters as it
+ *    changes) and each of its options carries a `visibleWhen` cascade predicate
+ *    (`record.country == 'cn'` …). The client offers only the matching options;
+ *    the objectql rule-validator (`evaluateOptionVisibility`, objectui#2284)
+ *    re-evaluates the SUBMITTED value against the merged record and rejects an
+ *    out-of-set one with `{ field, code: 'invalid_option' }` — client hiding is
+ *    UX, not a security boundary.
+ *
+ *  - `tier` carries one ROLE-GATED option: `restricted` is offered only when
+ *    `'admin' in current_user.positions`. The same rule-validator rejects a
+ *    non-admin who submits it anyway; it fails open only when `current_user` is
+ *    unbound (a system write) — the acting user is bound from the request on
+ *    authenticated writes (engine `buildEvalUser`).
+ *
+ * `sharingModel: 'public_read_write'` so the seeded admin (and the live e2e,
+ * objectui `e2e/live/cascading-options.spec.ts`) can create records without a
+ * bespoke permission set; belonging to no permission set, it is intentionally
+ * absent from the ADR-0090 access-matrix snapshot.
+ *
+ * The server verdict is unit-covered by objectql
+ * `rule-validator.option-visibility.test.ts`; this object is the served fixture
+ * the browser/API e2e drives. Predicates use the `P` (CEL) tag — the same
+ * authoring shape as the field-level `visibleWhen` on showcase_invoice.
+ */
+export const CascadingSelect = ObjectSchema.create({
+  name: 'showcase_cascade',
+  // [ADR-0090 D1] Explicit grandfather stamp: this demo object is intentionally
+  // world-writable (the live e2e creates against it); without the explicit OWD
+  // the secure default (unset => private) would owner-filter it.
+  sharingModel: 'public_read_write',
+  label: 'Cascading Select',
+  pluralLabel: 'Cascading Selects',
+  icon: 'git-fork',
+  description:
+    'B3 dynamic-options fixture: a country → province cascade (per-option visibleWhen + dependsOn) plus a role-gated tier, enforced client-side (offered set) AND server-side (objectql rejects an out-of-set submit).',
+
+  fields: {
+    name: Field.text({ label: 'Label', required: true, searchable: true, maxLength: 120 }),
+
+    country: Field.select({
+      label: 'Country',
+      options: [
+        { label: 'China', value: 'cn' },
+        { label: 'United States', value: 'us' },
+      ],
+    }),
+
+    // Dependent (cascading) options: gated until `country` is set, then filtered
+    // by each option's `visibleWhen`. `dependsOn` drives the form's gate +
+    // refresh; the per-option `visibleWhen` is the actual rule the client filters
+    // on AND the server enforces. Same predicate shape as the objectui catalog
+    // example (`fields-select/cascading-options`).
+    province: Field.select({
+      label: 'Province / State',
+      dependsOn: ['country'],
+      options: [
+        { label: 'Zhejiang', value: 'zj', visibleWhen: P`record.country == 'cn'` },
+        { label: 'Guangdong', value: 'gd', visibleWhen: P`record.country == 'cn'` },
+        { label: 'California', value: 'ca', visibleWhen: P`record.country == 'us'` },
+        { label: 'Texas', value: 'tx', visibleWhen: P`record.country == 'us'` },
+      ],
+    }),
+
+    // Role-gated option: `restricted` is offered only to admins. The client hides
+    // it for everyone else; the server rejects a non-admin who submits it anyway
+    // (`current_user` is bound from the request on authenticated writes).
+    tier: Field.select({
+      label: 'Tier',
+      options: [
+        { label: 'Standard', value: 'standard', default: true },
+        { label: 'Restricted (admin only)', value: 'restricted', visibleWhen: P`'admin' in current_user.positions` },
+      ],
+    }),
+  },
+});
diff --git a/examples/app-showcase/src/data/objects/index.ts b/examples/app-showcase/src/data/objects/index.ts
index 9b2f2b558b..2487c2b029 100644
--- a/examples/app-showcase/src/data/objects/index.ts
+++ b/examples/app-showcase/src/data/objects/index.ts
@@ -8,6 +8,7 @@ export { BusinessUnit } from './business-unit.object.js';
 export { Team, ProjectMembership } from './team.object.js';
 export { Product, Invoice, InvoiceLine } from './invoice.object.js';
 export { FieldZoo } from './field-zoo.object.js';
+export { CascadingSelect } from './cascading-select.object.js';
 export { Preference } from './preference.object.js';
 export { PrivateNote } from './private-note.object.js';
 export { Announcement } from './announcement.object.js';
diff --git a/examples/app-showcase/src/ui/apps/index.ts b/examples/app-showcase/src/ui/apps/index.ts
index 21e57d7023..721f67d61a 100644
--- a/examples/app-showcase/src/ui/apps/index.ts
+++ b/examples/app-showcase/src/ui/apps/index.ts
@@ -57,6 +57,9 @@ export const ShowcaseApp = App.create({
         { id: 'nav_categories', type: 'object', objectName: 'showcase_category', label: 'Categories', icon: 'list-tree' },
         { id: 'nav_business_units', type: 'object', objectName: 'showcase_business_unit', label: 'Business Units', icon: 'network' },
         { id: 'nav_field_zoo', type: 'object', objectName: 'showcase_field_zoo', label: 'Field Zoo', icon: 'shapes' },
+        // B3 (#1583) dynamic-options fixture: country → province cascade + a
+        // role-gated tier, enforced server-side by the objectql rule path.
+        { id: 'nav_cascade', type: 'object', objectName: 'showcase_cascade', label: 'Cascading Select', icon: 'git-fork' },
       ],
     },
     {