@@ -36,4 +36,31 @@ sockets, CI-stable). Tests act as a browser client would: sign in, hit
 4. **Prove it catches the bug**: temporarily revert the relevant fix and confirm
    the test goes red. A green-on-the-bug test is not a gate.
 
+## Capability matrix (the AI-authoring angle)
+
+This is a **development platform**: third parties have an AI author arbitrary
+metadata. The risk is not "a platform change broke the CRM example" — it's "the
+AI used a valid primitive the examples don't exercise, and it silently breaks at
+runtime." So beyond pinning the example apps, the gate is growing into a
+**capability matrix**: every authorable primitive gets a runtime round-trip
+proof.
+
+`test/field-zoo-roundtrip.dogfood.test.ts` is the first block — it writes one
+record covering many field types over the real REST API and asserts each reads
+back with type fidelity. On its first run it surfaced three real gaps
+(`rating`/`slider`/`toggle` read back as strings), which are **quarantined**, not
+hidden:
+
+```ts
+// Known type-fidelity gap → it.fails passes while broken and turns RED the day
+// it's fixed, forcing the quarantine to be lifted instead of rotting.
+const runner = c.xfail ? it.fails : it;
+```
+
+Roadmap (each its own slice, see the ADR): flow-node matrix, form-widget matrix,
+RLS-pattern matrix; then a generative pass that emits random valid metadata from
+the spec's zod surface; then run the AI **template corpus** through the harness.
+The binding policy — every authorable+live primitive must carry a runtime proof
+— is the subject of a dedicated ADR.
+
 Runs in CI as the `Dogfood Regression Gate` job (and under `turbo run test`).
@@ -20,7 +20,8 @@
     "@objectstack/plugin-security": "workspace:*",
     "@objectstack/service-settings": "workspace:*",
     "@objectstack/service-analytics": "workspace:*",
-    "@objectstack/example-crm": "workspace:*"
+    "@objectstack/example-crm": "workspace:*",
+    "@objectstack/example-showcase": "workspace:*"
   },
   "devDependencies": {
     "@types/node": "^25.9.3",
 
@@ -0,0 +1,132 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+//
+// CAPABILITY-MATRIX golden test — every authorable field type must survive a
+// real HTTP write → read round-trip.
+//
+// `showcase_field_zoo` carries one field of (almost) every protocol FieldType.
+// Until now it was only *static*-checked (the metadata bundle registers it);
+// nothing wrote a record and read it back. But the platform's value is that an
+// AI can author ANY field and it works at runtime — so each field type needs a
+// runtime proof, not a shape assertion. This is the first block of that matrix
+// and the direct guard for #2004 (array-typed fields silently failed to persist;
+// Field.time rejected time-of-day).
+
+import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import showcaseStack from '@objectstack/example-showcase';
+import { bootDogfoodStack, type DogfoodStack } from '../src/harness.js';
+
+// A field-type coverage entry. `write` is the value POSTed; `expect` describes
+// how the value must come back. `equal` = exact (or set-equal for arrays);
+// `computed`/`present` cover server-owned fields you don't write.
+type Check =
+  | { kind: 'equal'; write: unknown }
+  | { kind: 'setEqual'; write: unknown[] }
+  | { kind: 'present' } // server-assigned, just must be non-null
+  | { kind: 'computed'; expected: unknown }; // derived, asserted not written
+
+interface FieldCase {
+  field: string;
+  type: string;
+  check: Check;
+  // KNOWN GAP: the schema→SQL-column mapping / read coercion doesn't yet cover
+  // this type, so it round-trips with the wrong JS type (e.g. '4' not 4). The
+  // value persists (no data loss), but fidelity leaks. Quarantined via it.fails
+  // so it stays visible AND auto-flags the day it's fixed. Tracked separately.
+  xfail?: boolean;
+}
+
+// The #2004 headliners are the three array types + f_time. The rest broaden the
+// matrix across scalars, temporals, structured JSON, and computed/system fields.
+const MATRIX: FieldCase[] = [
+  // text-ish
+  { field: 'f_textarea', type: 'textarea', check: { kind: 'equal', write: 'line1\nline2' } },
+  { field: 'f_email', type: 'email', check: { kind: 'equal', write: 'zoo@example.com' } },
+  { field: 'f_url', type: 'url', check: { kind: 'equal', write: 'https://objectstack.ai' } },
+  { field: 'f_phone', type: 'phone', check: { kind: 'equal', write: '+14155550123' } },
+  // numbers
+  { field: 'f_number', type: 'number', check: { kind: 'equal', write: 42 } },
+  { field: 'f_currency', type: 'currency', check: { kind: 'equal', write: 1234.56 } },
+  { field: 'f_percent', type: 'percent', check: { kind: 'equal', write: 75 } },
+  { field: 'f_rating', type: 'rating', check: { kind: 'equal', write: 4 }, xfail: true },
+  { field: 'f_slider', type: 'slider', check: { kind: 'equal', write: 25 }, xfail: true },
+  // temporal — f_time is a #2004 fix (time-of-day)
+  { field: 'f_date', type: 'date', check: { kind: 'equal', write: '2024-03-15' } },
+  { field: 'f_time', type: 'time', check: { kind: 'equal', write: '14:30:00' } },
+  // logic
+  { field: 'f_boolean', type: 'boolean', check: { kind: 'equal', write: true } },
+  { field: 'f_toggle', type: 'toggle', check: { kind: 'equal', write: true }, xfail: true },
+  // scalar selection
+  { field: 'f_select', type: 'select', check: { kind: 'equal', write: 'high' } },
+  { field: 'f_radio', type: 'radio', check: { kind: 'equal', write: 'yes' } },
+  // ── #2004 array headliners — these silently dropped before the fix ──
+  { field: 'f_multiselect', type: 'multiselect', check: { kind: 'setEqual', write: ['red', 'blue'] } },
+  { field: 'f_checkboxes', type: 'checkboxes', check: { kind: 'setEqual', write: ['email', 'push'] } },
+  { field: 'f_tags', type: 'tags', check: { kind: 'setEqual', write: ['alpha', 'beta', 'gamma'] } },
+  // structured JSON
+  { field: 'f_json', type: 'json', check: { kind: 'equal', write: { a: 1, b: [2, 3] } } },
+  { field: 'f_color', type: 'color', check: { kind: 'equal', write: '#FF8800' } },
+  // computed / system — not written, must materialize
+  { field: 'f_autonumber', type: 'autonumber', check: { kind: 'present' } },
+  // f_number(42) * f_percent(75) / 100 = 31.5
+  { field: 'f_formula', type: 'formula', check: { kind: 'computed', expected: 31.5 } },
+];
+
+describe('dogfood: field-type capability matrix round-trips over HTTP (#2004)', () => {
+  let stack: DogfoodStack;
+  let record: Record<string, unknown>;
+
+  beforeAll(async () => {
+    stack = await bootDogfoodStack(showcaseStack);
+    const token = await stack.signIn();
+
+    // Build the create body from every `equal`/`setEqual` entry (+ required name).
+    const body: Record<string, unknown> = { name: 'zoo-roundtrip' };
+    for (const c of MATRIX) {
+      if (c.check.kind === 'equal') body[c.field] = c.check.write;
+      else if (c.check.kind === 'setEqual') body[c.field] = c.check.write;
+    }
+
+    const created = await stack.apiAs(token, 'POST', '/data/showcase_field_zoo', body);
+    expect(created.status, `create failed: ${created.status} ${await created.clone().text()}`).toBeLessThan(300);
+    const createdJson = (await created.json()) as { id?: string; record?: { id?: string } };
+    const id = createdJson.id ?? createdJson.record?.id;
+    expect(id, 'no id returned from create').toBeTruthy();
+
+    const got = await stack.apiAs(token, 'GET', `/data/showcase_field_zoo/${id}`);
+    expect(got.status).toBe(200);
+    const gotJson = (await got.json()) as { record?: Record<string, unknown> } & Record<string, unknown>;
+    record = (gotJson.record ?? gotJson) as Record<string, unknown>;
+  }, 60_000);
+
+  afterAll(async () => {
+    await stack?.stop();
+  });
+
+  for (const c of MATRIX) {
+    // xfail entries are KNOWN type-fidelity gaps: `it.fails` passes while the
+    // assertion throws and turns RED the moment the gap is fixed — forcing the
+    // quarantine to be lifted rather than silently rotting.
+    const runner = c.xfail ? it.fails : it;
+    runner(`${c.type} (${c.field}) round-trips`, () => {
+      const actual = record[c.field];
+      switch (c.check.kind) {
+        case 'equal':
+          expect(actual).toEqual(c.check.write);
+          break;
+        case 'setEqual': {
+          // Array-typed fields: persisted as a JSON array; order is not
+          // guaranteed, so compare as sets (the #2004 break returned null/[]).
+          expect(Array.isArray(actual), `${c.field} not an array: ${JSON.stringify(actual)}`).toBe(true);
+          expect([...(actual as unknown[])].sort()).toEqual([...c.check.write].sort());
+          break;
+        }
+        case 'present':
+          expect(actual ?? null, `${c.field} should be server-assigned`).not.toBeNull();
+          break;
+        case 'computed':
+          expect(Number(actual)).toBeCloseTo(Number(c.check.expected), 5);
+          break;
+      }
+    });
+  }
+});