@@ -0,0 +1,14 @@
+---
+'@object-ui/app-shell': patch
+---
+
+fix(app-shell): the Studio API tab's example body leaves out `owner_id` and optional reference fields, so the copied Create and Update calls are accepted
+
+Clause-②: no
+Metadata-protocol: none
+
+The API tab of an object in Studio showed an example body that put the id `"related_record_id"` into every reference field, and added the platform's `owner_id` whenever there was room. That id names no record, so the copied Create (`POST`) and Update (`PATCH`) cURL were refused `400` with `reference_not_found` on nearly every object.
+
+- **Left out of the body:** every optional reference field (`lookup`, `master_detail`, `user`, `tree`) and every field the platform adds (`system: true`, such as `owner_id`, which the platform fills in when it is left out). The note under the body names them with the other optional fields not shown.
+- **A required reference** is still in the body, because a create without it is refused. Its value is now a placeholder in the same form as the cURL's `<token>`, naming the object whose record id goes there, such as `<id of a showcase_project record>`.
+- **Unchanged:** the other fields, their sample values, the order (required fields first) and the cap of eight fields.
@@ -31,7 +31,12 @@ import '@testing-library/jest-dom/vitest';
 import * as React from 'react';
 import { afterEach, describe, expect, it, vi } from 'vitest';
 import { cleanup, fireEvent, render, screen, waitFor } from '@testing-library/react';
-import { valueSchemaFor, type ValueShapeFieldDef } from '@objectstack/spec/data';
+import {
+  REFERENCE_VALUE_TYPES,
+  referenceTargetOf,
+  valueSchemaFor,
+  type ValueShapeFieldDef,
+} from '@objectstack/spec/data';
 import { isValueDomainMember, type ValueDomain } from '@objectstack/spec/shared';
 
 import { ObjectApiPanel } from './ObjectApiPanel';
@@ -196,15 +201,20 @@ describe('ObjectApiPanel example body: values the write path accepts (objectui#1
         expect(body, name).not.toHaveProperty(name);
         continue;
       }
-      expect(body, name).toHaveProperty(name);
-      const parsed = storedParse(def, body[name]);
-      expect(parsed.success, `${name} (${String(def.type)}) = ${JSON.stringify(body[name])}`).toBe(true);
+      // An optional reference never joins the body (objectstack#27490); its
+      // value shape is read with the field required.
+      const shownDef = REFERENCE_VALUE_TYPES.has(String(def.type)) ? { ...def, required: true } : def;
+      const value = shownDef === def ? body[name] : shownBody({ [name]: shownDef })[name];
+      cleanup();
+      expect(value, name).toBeDefined();
+      const parsed = storedParse(shownDef, value);
+      expect(parsed.success, `${name} (${String(def.type)}) = ${JSON.stringify(value)}`).toBe(true);
     }
   });
 
   it('a multi-valued field shows an array of one element', () => {
     const body = shownBody({
-      f_lookups: ZOO_FIELDS.f_lookups,
+      f_lookups: { ...ZOO_FIELDS.f_lookups, required: true },
       f_multiselect: ZOO_FIELDS.f_multiselect,
       f_tags: ZOO_FIELDS.f_tags,
       f_files: { type: 'file', label: 'Files', multiple: true },
@@ -289,3 +299,80 @@ describe('ObjectApiPanel copied cURL (objectui#11803)', () => {
     expect(copied).toContain(`-d '${JSON.stringify(body)}'`);
   });
 });
+
+/**
+ * The body the write path accepts as it stands — objectstack#27490.
+ *
+ * The defect: every reference field showed the id `"related_record_id"`, which
+ * names no record, and the platform-added `owner_id` joined the body whenever
+ * there was room under the cap, so the copied Create and Update calls were
+ * refused `reference_not_found` on nearly every object.
+ *
+ * The oracle is the write path's own reference check (`assertReferencesResolve`
+ * in `@objectstack/objectql`): it resolves a supplied value only on a field
+ * `referenceTargetOf` answers a target for, so a body in which no field has
+ * one leaves that check nothing to refuse, and every value still parses under
+ * the stored-form contract.
+ */
+describe('ObjectApiPanel example body: no record id to look up (objectstack#27490)', () => {
+  function expectAcceptedAsItStands(fields: Record<string, Def>) {
+    const body = shownBody(fields);
+    for (const [name, value] of Object.entries(body)) {
+      const def = fields[name];
+      expect(referenceTargetOf(def), `${name} names a record`).toBeUndefined();
+      expect(storedParse(def, value).success, `${name} = ${JSON.stringify(value)}`).toBe(true);
+    }
+    return body;
+  }
+
+  it('leaves owner_id out even when the body has room for it, and says so', () => {
+    const body = expectAcceptedAsItStands(served({ name: { type: 'text', label: 'Name' } }));
+    expect(body).toEqual({ name: 'string' });
+    expect(screen.getByText(/owner_id/)).toBeInTheDocument();
+  });
+
+  it('still names the fields it left out when none of them is shown', () => {
+    const body = shownBody(served({ account: { type: 'lookup', label: 'Account', reference: 'showcase_account' } }));
+    expect(body).toEqual({});
+    expect(screen.getByText(/Optional fields not shown: owner_id, account/)).toBeInTheDocument();
+  });
+
+  it('leaves every optional reference out (showcase Account and field zoo)', () => {
+    expectAcceptedAsItStands(served(ACCOUNT_FIELDS));
+    cleanup();
+    const zoo = Object.fromEntries(Object.entries(ZOO_FIELDS).filter(([n]) => n !== 'f_master_detail'));
+    const body = expectAcceptedAsItStands(served(zoo));
+    expect(Object.keys(body)).toContain('name');
+    const omitted = screen.getByText(/Optional fields not shown/).textContent ?? '';
+    for (const ref of ['owner_id', 'f_lookup', 'f_lookups', 'f_tree', 'f_user', 'f_users']) {
+      expect(omitted, ref).toContain(ref);
+    }
+  });
+
+  it('shows a required reference as a placeholder naming its target, never as an id', () => {
+    const body = shownBody(served(ZOO_FIELDS));
+    expect(body.f_master_detail).toBe('<id of a showcase_project record>');
+    cleanup();
+    const user = shownBody({ assignee: { type: 'user', label: 'Assignee', required: true } });
+    expect(user.assignee).toBe('<id of a sys_user record>');
+  });
+
+  it('the copied Create and Update calls carry the same body, without owner_id', async () => {
+    const writeText = vi.fn(async (_text: string) => {});
+    Object.defineProperty(navigator, 'clipboard', { value: { writeText }, configurable: true });
+    const body = expectAcceptedAsItStands(served(ACCOUNT_FIELDS));
+    const rows = screen.getAllByTitle('Copy as cURL');
+    // Endpoint rows: list, create (POST), get, update (PATCH), delete.
+    fireEvent.click(rows[1]);
+    await waitFor(() => expect(writeText).toHaveBeenCalledTimes(1));
+    fireEvent.click(rows[3]);
+    await waitFor(() => expect(writeText).toHaveBeenCalledTimes(2));
+    const [create, update] = writeText.mock.calls.map(([text]) => text);
+    expect(create).toContain('-X POST');
+    expect(update).toContain('-X PATCH');
+    for (const copied of [create, update]) {
+      expect(copied).toContain(`-d '${JSON.stringify(body)}'`);
+      expect(copied).not.toContain('owner_id');
+    }
+  });
+});
@@ -20,8 +20,9 @@
  * cross-cutting concern that belongs in a global Developer console, not on a
  * per-object tab. This panel derives its example body from the object's DRAFT
  * fields, so it stays in sync with unpublished schema edits: each value is one
- * the write path accepts for that field's type (objectui#11803), and the
- * copied cURL carries the `Authorization` header the call needs.
+ * the write path accepts for that field's type (objectui#11803), the body names
+ * no record the reader would have to look up unless a required field needs one,
+ * and the copied cURL carries the `Authorization` header the call needs.
  */
 
 import React from 'react';
@@ -39,6 +40,7 @@ import {
   SINGLE_OPTION_TYPES,
   STRING_VALUE_TYPES,
   isMultiValueField,
+  referenceTargetOf,
   type FieldType,
 } from '@objectstack/spec/data';
 import type { ValueDomain } from '@objectstack/spec/shared';
@@ -154,8 +156,12 @@ function exampleElementFor(type: string, def: FieldDef): unknown {
     return firstOptionCode(def) ?? TEXT_SAMPLE;
   }
   // A reference stores the related record's id; a media field the id of an
-  // uploaded file (`sys_file`), never an inline object or a URL.
-  if (REFERENCE_VALUE_TYPES.has(type)) return 'related_record_id';
+  // uploaded file (`sys_file`), never an inline object or a URL. The write path
+  // refuses an id that names no record of the target, so a reference sample
+  // cannot be a working value: it is a placeholder no reader takes for one,
+  // naming the object whose id goes there. Only a required reference reaches
+  // the body at all (`buildExampleBody`).
+  if (REFERENCE_VALUE_TYPES.has(type)) return referencePlaceholderFor(def);
   if (FILE_REFERENCE_TYPES.has(type)) return 'file_id';
   switch (type) {
     case 'location':
@@ -175,6 +181,12 @@ function exampleElementFor(type: string, def: FieldDef): unknown {
   }
 }
 
+/** The placeholder a required reference field shows, in the cURL token's `<...>` form. */
+function referencePlaceholderFor(def: FieldDef): string {
+  const target = referenceTargetOf(def);
+  return target ? `<id of a ${target} record>` : '<id of the related record>';
+}
+
 /** The example value for one field: an array of one element when the field is multi-valued. */
 function exampleValueFor(def: FieldDef): unknown {
   const type = String(def.type);
@@ -185,27 +197,35 @@ function exampleValueFor(def: FieldDef): unknown {
 /**
  * An example create body from the object's writable draft fields, in the order
  * an author needs them: every required field first, then optional fields up to
- * {@link EXAMPLE_FIELD_CAP} — the object's own fields before the ones the
- * platform adds (`system: true`, such as `owner_id`, which the platform fills
- * in when it is left out). Computed, read-only and hidden fields are skipped.
- * `omitted` names the optional fields left out, so the panel can say so.
+ * {@link EXAMPLE_FIELD_CAP}. Computed, read-only and hidden fields are skipped.
+ *
+ * Two kinds of optional field never join the body, so a copied call with no
+ * required reference is accepted as it stands:
+ * - a field the platform adds (`system: true`, such as `owner_id`), which the
+ *   platform fills in when it is left out;
+ * - a reference field, whose value must be the id of an existing record of its
+ *   target — no sample can be one, and the write path refuses an id that
+ *   names no record.
+ * `omitted` names every optional field left out, these included, so the panel
+ * can say so.
  */
 function buildExampleBody(fields: unknown): { body: Record<string, unknown>; omitted: string[] } {
   const writable = readFields(fields).entries.filter(({ def }) => {
     if (COMPUTED_VALUE_TYPES.has(String(def.type))) return false;
     return def.readonly !== true && def.hidden !== true;
   });
   const required = writable.filter(({ def }) => def.required === true);
-  const optional = [
-    ...writable.filter(({ def }) => def.required !== true && def.system !== true),
-    ...writable.filter(({ def }) => def.required !== true && def.system === true),
-  ];
+  const optional = writable.filter(({ def }) => def.required !== true);
+  const neverShown = ({ def }: (typeof optional)[number]) =>
+    def.system === true || REFERENCE_VALUE_TYPES.has(String(def.type));
+  const showable = optional.filter((entry) => !neverShown(entry));
   const room = Math.max(0, EXAMPLE_FIELD_CAP - required.length);
-  const shown = [...required, ...optional.slice(0, room)];
+  const shown = [...required, ...showable.slice(0, room)];
   // `Object.fromEntries` defines own properties, so a field named `__proto__`
   // (a legal field name) is kept rather than swallowed by assignment.
   const body = Object.fromEntries(shown.map(({ name, def }) => [name, exampleValueFor(def)]));
-  return { body, omitted: optional.slice(room).map(({ name }) => name) };
+  const omitted = [...showable.slice(room), ...optional.filter(neverShown)];
+  return { body, omitted: omitted.map(({ name }) => name) };
 }
 
 export function ObjectApiPanel({
@@ -273,7 +293,7 @@ export function ObjectApiPanel({
         ))}
       </div>
 
-      {Object.keys(exampleBody).length > 0 && (
+      {(Object.keys(exampleBody).length > 0 || omitted.length > 0) && (
         <div className="rounded-lg border">
           <header className="border-b px-3 py-1.5 text-[11px] font-medium text-muted-foreground">
             {t('engine.studio.api.body', locale)}