diff --git a/ui/packages/app-shell/src/views/metadata-admin/inspectors/PageBlockInspector.jsonFieldLabel-27178.test.tsx b/ui/packages/app-shell/src/views/metadata-admin/inspectors/PageBlockInspector.jsonFieldLabel-27178.test.tsx
new file mode 100644
index 00000000000..f3d0a5b66cb
--- /dev/null
+++ b/ui/packages/app-shell/src/views/metadata-admin/inspectors/PageBlockInspector.jsonFieldLabel-27178.test.tsx
@@ -0,0 +1,102 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * The page block inspector's JSON editor (`InspectorJsonField`) is named by the
+ * label drawn above it: `Label htmlFor` ↔ textarea `id`, the pairing the
+ * inspector's other rows already carry. Without it every curated JSON prop
+ * exposed an unnamed text box to a screen reader, and `getByLabelText` found
+ * the label but "no form control … associated to that label".
+ *
+ * Both doors that draw the editor are read through their label here:
+ *  - a curated `kind: 'json'` prop (`record:related_list.add`), unset, which is
+ *    the only door that can ADD the key;
+ *  - the JSON fallback for a stored value in another arm of a union
+ *    (`record:related_list.sort` stored as a string).
+ * Two editors in one panel each resolve to their own textarea.
+ */
+
+import '@testing-library/jest-dom/vitest';
+import * as React from 'react';
+import { describe, it, expect, vi, afterEach } from 'vitest';
+import { render, screen, fireEvent, cleanup } from '@testing-library/react';
+
+// The filter builder lives inside a Radix popover, which does not open in
+// jsdom; the popover parts render inline (this directory's existing way).
+vi.mock('@object-ui/components', async () => {
+  const actual = await vi.importActual<Record<string, unknown>>('@object-ui/components');
+  const Pass = ({ children }: { children?: unknown }) => children as never;
+  return { ...actual, Popover: Pass, PopoverTrigger: Pass, PopoverContent: Pass };
+});
+vi.mock('../previews/useObjectFields', () => ({
+  useObjectFields: () => ({
+    fields: [{ name: 'subject', label: 'Subject', type: 'text', hidden: false }],
+    loading: false,
+    error: null,
+  }),
+}));
+vi.mock('../useMetadata', () => ({
+  useMetadataClient: () => ({ get: vi.fn(async () => undefined), list: vi.fn(async () => [] as unknown[]) }),
+}));
+
+import { PageBlockInspector } from './PageBlockInspector';
+
+afterEach(() => cleanup());
+
+type Row = Record<string, unknown>;
+
+function Host({ props, writes }: { props: Row; writes: Row[] }) {
+  const [draft, setDraft] = React.useState<Row>({
+    name: 'lead_page',
+    type: 'record',
+    object: 'lead',
+    kind: 'full',
+    regions: [{ name: 'main', components: [{ id: 'tasks', type: 'record:related_list', properties: props }] }],
+  });
+  return (
+    <PageBlockInspector
+      type="page"
+      name="lead_page"
+      draft={draft}
+      selection={{ kind: 'block', id: 'regions[0].components[0]' }}
+      onPatch={(patch: Row) => setDraft((d) => {
+        const next = { ...d, ...patch };
+        const regions = next.regions as Array<{ components: Array<{ properties: Row }> }>;
+        writes.push(regions[0].components[0].properties);
+        return next;
+      })}
+      onClearSelection={() => {}}
+      readOnly={false}
+      locale="en-US"
+    />
+  );
+}
+
+const BASE = { objectName: 'task', relationshipField: 'lead' };
+const ADD_LABEL = 'Add existing records (picker)';
+
+describe('page block inspector — the JSON editor is named by its label', () => {
+  it('finds a curated JSON prop by its label, and the textarea it finds is the editor', () => {
+    const writes: Row[] = [];
+    render(<Host props={BASE} writes={writes} />);
+    const box = screen.getByLabelText(ADD_LABEL);
+    expect(box.tagName).toBe('TEXTAREA');
+    expect(box).toHaveAccessibleName(ADD_LABEL);
+
+    const add = { picker: { object: 'sys_user' }, linkField: 'user_id' };
+    fireEvent.change(box, { target: { value: JSON.stringify(add) } });
+    fireEvent.blur(box);
+    expect(writes.at(-1)!.add).toEqual(add);
+  });
+
+  it('names the JSON fallback of a stored other-arm value, and each editor keeps its own id', () => {
+    render(<Host props={{ ...BASE, sort: 'subject' }} writes={[]} />);
+    const sort = screen.getByLabelText('Sort');
+    expect(sort.tagName).toBe('TEXTAREA');
+    expect((sort as HTMLTextAreaElement).value).toBe('"subject"');
+
+    const add = screen.getByLabelText(ADD_LABEL);
+    expect(add).not.toBe(sort);
+    expect(sort.id).not.toBe('');
+    expect(add.id).not.toBe(sort.id);
+  });
+});
diff --git a/ui/packages/app-shell/src/views/metadata-admin/inspectors/PageBlockInspector.tsx b/ui/packages/app-shell/src/views/metadata-admin/inspectors/PageBlockInspector.tsx
index 97cdc540f09..e552a33e1ea 100644
--- a/ui/packages/app-shell/src/views/metadata-admin/inspectors/PageBlockInspector.tsx
+++ b/ui/packages/app-shell/src/views/metadata-admin/inspectors/PageBlockInspector.tsx
@@ -180,6 +180,10 @@ function InspectorJsonField({ label, value, onCommit, disabled, placeholder, loc
   // message is resolved at render and follows a locale switch instead of
   // freezing whatever language was active when the parse failed.
   const [invalid, setInvalid] = React.useState(false);
+  // Minted here, not derived from the label or the prop name: `renderField`
+  // draws this editor inside array rows too, where a caller-derived id would
+  // repeat and `for` would resolve to the first row's textarea.
+  const id = React.useId();
   React.useEffect(() => { setText(initial); setInvalid(false); }, [initial]);
   const commit = () => {
     if (disabled) return;
@@ -195,8 +199,9 @@ function InspectorJsonField({ label, value, onCommit, disabled, placeholder, loc
   };
   return (
     <div className="space-y-1">
-      <Label className="text-xs text-muted-foreground">{label}</Label>
+      <Label htmlFor={id} className="text-xs text-muted-foreground">{label}</Label>
       <textarea
+        id={id}
         value={text}
         onChange={(e) => setText(e.target.value)}
         onBlur={commit}