@@ -0,0 +1,7 @@
+---
+'@objectstack/rest': patch
+---
+
+Public forms on a walled tenancy posture: a form whose object is walled by an organization column is no longer offered to anonymous visitors. An anonymous submission carries no organization, and on a walled posture an insert into such an object without one is refused, so the form used to render and then answer `500 ERR_SYSTEM_WRITE_ORGANIZATION_REQUIRED` on every submit. Both anonymous form endpoints (`GET /forms/:slug` and `POST /forms/:slug/submit`) now answer it exactly as they answer a withdrawn form (`404 FORM_NOT_FOUND`), so an anonymous caller learns nothing about the deployment's tenancy. The administrator's read of the form (`GET /meta/view/:name`) states why in `_diagnostics.warnings`, located at the form's `sharing`, with the remedy: if the object's rows belong to no organization, declare `tenancy: { enabled: false }` on it. Forms bound to tenancy-disabled objects, and single-posture deployments, are unchanged.
+
+Clause-②: no
@@ -162,6 +162,10 @@ describe('walled posture: withdrawing a public form from anonymous intake', () =
     const p = await probe();
     expect([p.get, p.submit]).toEqual([200, 201]);
     expect(p.landed).toHaveLength(1);
+    // [#21476] The control of `showcase-public-form-walled-intake.dogfood.test.ts`:
+    // a tenancy-disabled object takes intake on a walled posture, so the
+    // administrator's read states no intake reason.
+    expect((await read())._diagnostics?.warnings).toBeUndefined();
   });
 
   it('withdrawn in an organization: refused 403 NOT_OVERRIDABLE naming the env-wide save, and nothing is saved', async () => {
 
@@ -0,0 +1,116 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+//
+// [#21476] On a WALLED tenancy posture the showcase's public contact form is
+// not offered, on a real boot.
+//
+// `showcase_inquiry.contact` publishes `/forms/contact-us`, and
+// `showcase_inquiry` is walled by the injected `organization_id`. An anonymous
+// submission carries no organization, and on a walled posture the engine
+// refuses an insert without one into a walled object. Before this pin the form
+// was served (`GET` 200) and every submit answered `500
+// ERR_SYSTEM_WRITE_ORGANIZATION_REQUIRED`. Pinned:
+//
+//   - both anonymous doors answer the not-found answer a withdrawn form gets,
+//     byte for byte (measured against the same form withdrawn env-wide on the
+//     same boot), and no `showcase_inquiry` row lands;
+//   - the administrator's read of the form names why, at `config.sharing`.
+//
+// The control (a form bound to a `tenancy: { enabled: false }` object on the
+// same walled posture is accepted, and its admin read carries no warning) is
+// `public-form-withdrawal-walled.dogfood.test.ts`.
+
+import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import showcaseStack from '@objectstack/example-showcase';
+import { bootStack, type VerifyStack } from '@objectstack/verify';
+import { SecurityPlugin, securityDefaultPermissionSets } from '@objectstack/plugin-security';
+
+const VIEW = '/meta/view/showcase_inquiry.contact';
+const SYS = { isSystem: true } as const;
+
+describe('showcase, walled posture: the public contact form is not offered, and the admin read says why', () => {
+  let stack: VerifyStack;
+  let admin: string;
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  let ql: any;
+  let probeSeq = 0;
+
+  /** Both anonymous doors' raw answers, plus the rows a submit with a unique marker left. */
+  const probe = async () => {
+    const marker = `walled_intake_probe_${++probeSeq}`;
+    const get = await stack.api('/forms/contact-us');
+    const submit = await stack.api('/forms/contact-us/submit', {
+      method: 'POST',
+      headers: { 'content-type': 'application/json' },
+      body: JSON.stringify({ name: marker, email: 'probe@example.com', message: 'probe' }),
+    });
+    const answers = [get.status, await get.text(), submit.status, await submit.text()];
+    const landed = await ql.find('showcase_inquiry', { where: { name: marker }, context: SYS });
+    return { answers, landed: landed as unknown[] };
+  };
+
+  /** The form as the administrator reads it. */
+  const read = async (): Promise<Record<string, any>> => {
+    const res = await stack.apiAs(admin, 'GET', VIEW);
+    expect(res.status).toBe(200);
+    const json = (await res.json()) as { item?: Record<string, any> };
+    return (json.item ?? json) as Record<string, any>;
+  };
+
+  /** Save the form env-wide (the admin has no active organization) with `allowAnonymous` set. */
+  const saveAllowAnonymous = async (published: Record<string, any>, allowAnonymous: boolean) => {
+    const body = structuredClone(published);
+    body.config.sharing.allowAnonymous = allowAnonymous;
+    const res = await stack.apiAs(admin, 'PUT', VIEW, body);
+    expect(res.status, await res.clone().text()).toBe(200);
+  };
+
+  beforeAll(async () => {
+    stack = await bootStack(showcaseStack, {
+      multiTenant: 'posture-only',
+      security: new SecurityPlugin({ defaultPermissionSets: [...securityDefaultPermissionSets] }),
+    });
+    admin = await stack.signIn();
+    ql = await stack.kernel.getServiceAsync('objectql');
+  }, 180_000);
+
+  afterAll(async () => {
+    await stack?.stop();
+  });
+
+  it('PRECONDITION: a walled posture in force, no organization for an anonymous request, the form published', async () => {
+    const tenancy = stack.tenancy();
+    expect(tenancy.posture).toBe('isolated');
+    expect(await tenancy.defaultOrgId()).toBeNull();
+    expect((await read()).config?.sharing).toMatchObject({ enabled: true, allowAnonymous: true });
+  });
+
+  it('both doors answer the withdrawn form\'s not-found answer byte for byte, and nothing lands', async () => {
+    const unavailable = await probe();
+    expect(unavailable.answers[0]).toBe(404);
+    expect(JSON.parse(unavailable.answers[1] as string).code).toBe('FORM_NOT_FOUND');
+    expect(unavailable.landed).toHaveLength(0);
+
+    const published = Object.fromEntries(Object.entries(await read()).filter(([k]) => !k.startsWith('_')));
+    await saveAllowAnonymous(published, false);
+    try {
+      const withdrawn = await probe();
+      expect(withdrawn.landed).toHaveLength(0);
+      expect(unavailable.answers).toEqual(withdrawn.answers);
+    } finally {
+      await saveAllowAnonymous(published, true);
+    }
+    // Republished, it is still not offered on this posture.
+    const again = await probe();
+    expect(again.answers).toEqual(unavailable.answers);
+    expect(again.landed).toHaveLength(0);
+  });
+
+  it('the administrator\'s read names why, located at the form\'s sharing', async () => {
+    const warnings = ((await read())._diagnostics?.warnings ?? []) as Array<{ path: string; message: string }>;
+    expect(warnings).toHaveLength(1);
+    expect(warnings[0].path).toBe('config.sharing');
+    for (const named of ['/forms/contact-us', "'showcase_inquiry'", "'organization_id'", "'isolated'"]) {
+      expect(warnings[0].message).toContain(named);
+    }
+  });
+});
@@ -0,0 +1,239 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+//
+// [#21476] One predicate decides whether an open public form can take an
+// anonymous submission on this deployment, and every door that serves the form
+// reads it. On a walled posture a form bound to an object walled by an
+// organization column used to be served and then answer `500
+// ERR_SYSTEM_WRITE_ORGANIZATION_REQUIRED` on every submit. Pinned: both doors
+// answer the withdrawn form's answer byte for byte and nothing is written; every
+// `/forms/` route is one of those doors; the controls are accepted; and the
+// administrator's read (both arms) names the reason, inside the validator.
+
+import { describe, it, expect, vi } from 'vitest';
+import { RestServer } from './rest-server';
+
+// [#10126] Pay the first transform of these dist-resolved workspace deps at
+// MODULE LOAD rather than inside a clocked `it()` body.
+import '@objectstack/spec/ui';
+
+const ORG = 'org_alpha';
+const SLUG = 'contact-us';
+
+function mockServer() {
+  return {
+    get: vi.fn(), post: vi.fn(), put: vi.fn(), delete: vi.fn(), patch: vi.fn(),
+    use: vi.fn(), listen: vi.fn().mockResolvedValue(undefined), close: vi.fn().mockResolvedValue(undefined),
+  };
+}
+
+function mockRes() {
+  const res: any = { statusCode: 200, body: undefined, headers: {} as Record<string, string> };
+  res.status = vi.fn((c: number) => { res.statusCode = c; return res; });
+  res.json = vi.fn((b: any) => { res.body = b; return res; });
+  res.header = vi.fn((k: string, v: string) => { res.headers[k] = v; return res; });
+  res.send = vi.fn(() => res);
+  res.end = vi.fn(() => res);
+  return res;
+}
+
+/** A flattened `viewKind: 'form'` item, as the protocol serves it. */
+const formView = (allowAnonymous = true) => ({
+  name: 'contact', object: 'inquiry', viewKind: 'form', _diagnostics: { valid: true },
+  config: {
+    data: { object: 'inquiry' },
+    sections: [{ fields: ['name', 'email'] }],
+    sharing: { enabled: true, allowAnonymous, publicLink: `/forms/${SLUG}` },
+  },
+});
+
+/** The bound object as the doors read it: the registry injects `organization_id`. */
+const inquiryObject = (tenancyDisabled: boolean) => ({
+  name: 'inquiry', label: 'Inquiry', ...(tenancyDisabled ? { tenancy: { enabled: false } } : {}),
+  fields: {
+    organization_id: { type: 'lookup', reference: 'sys_organization' },
+    name: { type: 'text', label: 'Name' },
+    email: { type: 'text', label: 'Email' },
+  },
+});
+
+/** Reproduces the registry's own "never registered" rejection. */
+const notRegistered = (): Error => Object.assign(new Error("Service 'tenancy' not found"), {
+  __objectstackServiceNotRegistered: true, code: 'SERVICE_NOT_REGISTERED', serviceName: 'tenancy',
+});
+
+type Tenancy = 'isolated' | 'group' | 'degraded' | 'single' | 'not-registered';
+
+/** `tenancyDisabled`: the control object (ADR-0066); `allowAnonymous: false`: the withdrawn reference; `cached`: the default admin-read arm. */
+interface Setup { tenancy: Tenancy; tenancyDisabled?: boolean; allowAnonymous?: boolean; cached?: boolean }
+
+function build(setup: Setup) {
+  const createData = vi.fn().mockResolvedValue({ object: 'inquiry', id: 'rec_1', record: {} });
+  const getMetaItems = vi.fn(async (req: { type: string }) => {
+    if (req.type === 'view') return [formView(setup.allowAnonymous ?? true)];
+    if (req.type === 'object') return [inquiryObject(setup.tenancyDisabled ?? false)];
+    return [];
+  });
+  const getMetaItemCached = vi.fn(async (_req: { cacheRequest: { ifNoneMatch?: string } }) => ({
+    data: formView(setup.allowAnonymous ?? true), etag: { value: 'v1', weak: false }, notModified: false,
+  }));
+  const protocol: any = {
+    getDiscovery: vi.fn().mockResolvedValue({ version: 'v0', routes: { data: '', metadata: '' } }),
+    getMetaTypes: vi.fn().mockResolvedValue([]),
+    getMetaItems,
+    getMetaItem: vi.fn(async ({ type, name }: any) => ({ type, name, item: formView(setup.allowAnonymous ?? true) })),
+    getMetaItemCached: setup.cached ? getMetaItemCached : undefined,
+    createData,
+  };
+  const tenancyServiceProvider = async () => {
+    switch (setup.tenancy) {
+      case 'isolated': return { posture: 'isolated', requestedPosture: 'isolated', defaultOrgId: async () => null };
+      case 'group': return { posture: 'group', requestedPosture: 'group', defaultOrgId: async () => null };
+      // A walled request the deployment cannot enforce: in force it is `single`.
+      case 'degraded': return { posture: 'single', requestedPosture: 'isolated', defaultOrgId: async () => null };
+      case 'single': return { posture: 'single', requestedPosture: 'single', defaultOrgId: async () => ORG };
+      case 'not-registered': throw notRegistered();
+    }
+  };
+  const rest = new RestServer(
+    mockServer() as any, protocol, { api: { requireAuth: false } } as any,
+    undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined,
+    undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined,
+    tenancyServiceProvider,
+  );
+  (rest as any).resolveExecCtx = async () => ({ userId: 'admin', systemPermissions: ['manage_metadata'] });
+  rest.registerRoutes();
+  const routes = rest.getRoutes();
+  const find = (method: string, path: string) => routes.find((r) => r.method === method && r.path === path)!;
+  const formDoors = routes.filter((r) => r.path.includes('/forms/'));
+  const drive = async (route: { handler: (req: any, res: any) => any }, method: string) => {
+    const res = mockRes();
+    const body = method === 'POST' ? { body: { name: 'x', email: 'x@example.com' } } : {};
+    await route.handler({ params: { slug: SLUG }, query: {}, headers: {}, ...body } as any, res);
+    return res;
+  };
+  return {
+    createData, getMetaItems, getMetaItemCached, formDoors, drive,
+    get: () => drive(find('GET', '/api/v1/forms/:slug'), 'GET'),
+    post: () => drive(find('POST', '/api/v1/forms/:slug/submit'), 'POST'),
+    async adminRead(headers: Record<string, string> = {}) {
+      const res = mockRes();
+      await find('GET', '/api/v1/meta/:type/:name').handler({ params: { type: 'view', name: 'contact' }, query: {}, headers } as any, res);
+      return res;
+    },
+  };
+}
+
+/** What the withdrawn form answers on a door — the shape an unavailable form must match byte for byte. */
+async function withdrawnAnswer(door: 'get' | 'post'): Promise<[number, string]> {
+  const s = build({ tenancy: 'isolated', allowAnonymous: false });
+  const res = await s[door]();
+  return [res.statusCode, JSON.stringify(res.body)];
+}
+
+const answer = (res: any): [number, string] => [res.statusCode, JSON.stringify(res.body)];
+
+describe('[#21476] a public form that cannot take intake on this posture is not offered', () => {
+  it('REFERENCE: the withdrawn form answers 404 FORM_NOT_FOUND on both doors', async () => {
+    const [getStatus, getBody] = await withdrawnAnswer('get');
+    const [postStatus, postBody] = await withdrawnAnswer('post');
+    expect([getStatus, JSON.parse(getBody).code]).toEqual([404, 'FORM_NOT_FOUND']);
+    expect([postStatus, JSON.parse(postBody).code]).toEqual([404, 'FORM_NOT_FOUND']);
+  });
+
+  // ENUMERATION: the doors are read off the registered routes, not listed by
+  // hand, and each door × walled posture is its own row.
+  const doors = build({ tenancy: 'isolated' }).formDoors;
+  it('ENUMERATION: the routes under /forms/ are exactly the two anonymous form doors', () => {
+    expect(doors.map((r) => `${r.method} ${r.path}`).sort())
+      .toEqual(['GET /api/v1/forms/:slug', 'POST /api/v1/forms/:slug/submit']);
+  });
+  for (const door of doors) {
+    for (const posture of ['isolated', 'group'] as const) {
+      it(`${door.method} ${door.path} · '${posture}', walled object: the withdrawn form's answer byte for byte, nothing written`, async () => {
+        const s = build({ tenancy: posture });
+        const route = s.formDoors.find((r) => r.method === door.method && r.path === door.path)!;
+        const expected = await withdrawnAnswer(door.method === 'POST' ? 'post' : 'get');
+        expect(answer(await s.drive(route, door.method))).toEqual(expected);
+        expect(s.createData).not.toHaveBeenCalled();
+      });
+    }
+  }
+
+  it('CONTROL: walled posture, object declared tenancy: { enabled: false } — accepted on both doors', async () => {
+    const s = build({ tenancy: 'isolated', tenancyDisabled: true });
+    const get = await s.get();
+    expect(get.statusCode).toBe(200);
+    expect(get.body.object).toBe('inquiry');
+    expect((await s.post()).statusCode).toBe(201);
+    expect(s.createData).toHaveBeenCalledTimes(1);
+  });
+
+  it('CONTROL: single posture, walled object — accepted, and the object is not even read for the predicate', async () => {
+    const s = build({ tenancy: 'single' });
+    expect((await s.post()).statusCode).toBe(201);
+    expect(s.getMetaItems.mock.calls.map(([r]) => r.type)).toEqual(['view']);
+  });
+
+  it('CONTROL: a degraded walled request reads the posture IN FORCE (single) — accepted', async () => {
+    const s = build({ tenancy: 'degraded' });
+    expect((await s.get()).statusCode).toBe(200);
+    expect((await s.post()).statusCode).toBe(201);
+  });
+
+  it('CONTROL: no tenancy service registered — no wall the doors can read, accepted', async () => {
+    const s = build({ tenancy: 'not-registered' });
+    expect((await s.get()).statusCode).toBe(200);
+    expect((await s.post()).statusCode).toBe(201);
+  });
+});
+
+describe('[#21476] the administrator\'s read names why intake is unavailable', () => {
+  for (const cached of [false, true]) {
+    const arm = cached ? 'cached arm' : 'uncached arm';
+
+    it(`${arm}: walled posture, walled object — a warning located at the form's sharing, naming the reason`, async () => {
+      const s = build({ tenancy: 'isolated', cached });
+      const res = await s.adminRead();
+      expect(res.statusCode).toBe(200);
+      const diagnostics = res.body.item._diagnostics;
+      expect(diagnostics.valid).toBe(true);
+      expect(diagnostics.warnings).toHaveLength(1);
+      expect(diagnostics.warnings[0].path).toBe('config.sharing');
+      const message: string = diagnostics.warnings[0].message;
+      for (const named of [`/forms/${SLUG}`, "'inquiry'", "'organization_id'", "'isolated'", 'tenancy: { enabled: false }']) {
+        expect(message).toContain(named);
+      }
+    });
+
+    it(`${arm}: CONTROL — tenancy-disabled object or single posture, no warning and _diagnostics untouched`, async () => {
+      for (const setup of [{ tenancy: 'isolated', tenancyDisabled: true }, { tenancy: 'single' }] as const) {
+        const res = await build({ ...setup, cached }).adminRead();
+        expect(res.statusCode).toBe(200);
+        expect(res.body.item._diagnostics).toEqual({ valid: true });
+      }
+    });
+  }
+
+  it('cached arm: the reason enters the validator — the bare protocol ETag revalidates into the reason, the folded one is 304', async () => {
+    const s = build({ tenancy: 'isolated', cached: true });
+    const first = await s.adminRead();
+    const etag = first.headers.ETag;
+    expect(etag).toMatch(/^"v1~[0-9a-f]{8}"$/);
+    expect(s.getMetaItemCached).toHaveBeenCalledTimes(1);
+    expect(s.getMetaItemCached.mock.calls[0]?.[0].cacheRequest).toEqual({ ifNoneMatch: undefined, ifModifiedSince: undefined });
+
+    const stale = await s.adminRead({ 'if-none-match': '"v1"' });
+    expect(stale.statusCode).toBe(200);
+    expect(stale.body.item._diagnostics.warnings).toHaveLength(1);
+
+    const fresh = await s.adminRead({ 'if-none-match': etag });
+    expect(fresh.statusCode).toBe(304);
+  });
+
+  it('cached arm: CONTROL — with no reason the validator is the protocol\'s own, and it still answers 304', async () => {
+    const s = build({ tenancy: 'isolated', tenancyDisabled: true, cached: true });
+    const first = await s.adminRead();
+    expect(first.headers.ETag).toBe('"v1"');
+    expect((await s.adminRead({ 'if-none-match': '"v1"' })).statusCode).toBe(304);
+  });
+});