diff --git a/.changeset/record-highlights-field-readonly.md b/.changeset/record-highlights-field-readonly.md
new file mode 100644
index 0000000000..8f09b7642c
--- /dev/null
+++ b/.changeset/record-highlights-field-readonly.md
@@ -0,0 +1,49 @@
+---
+"@objectstack/spec": minor
+---
+
+feat(spec): `RecordHighlightsField` declares `readonly` (#5176)
+
+The object form of a `record:highlights` entry now declares an optional
+`readonly: boolean`. It marks a highlight chip as non-editable — use it for
+columns a hook or automation maintains, which must not be hand-edited from the
+record header.
+
+```ts
+{
+  type: 'record:highlights',
+  properties: {
+    fields: [
+      'name',
+      { name: 'supply_share', type: 'number', readonly: true },
+    ],
+  },
+}
+```
+
+**Why this is a spec change and not a renderer detail.** The renderer's
+`HeaderHighlight` gate already refuses inline editing on a chip carrying
+`readonly`, but the key was not declared here — and the object member is not
+`.strict()`, so `RecordHighlightsField` **silently stripped** it:
+
+```
+input   { fields: [ { name: 'supply_share', readonly: true, type: 'number' } ] }
+parsed  { fields: [ { name: 'supply_share', type: 'number' } ] }
+```
+
+That worked end to end only because per-component props are not parsed on the
+live load path today (`PageComponentSchema.properties` is
+`z.record(z.string(), z.unknown())`, so the bag rides through untouched). The
+moment that gate is wired up, an authored `readonly` becomes either a silent
+strip — a machine-owned column quietly editable again, with no diagnostic
+anywhere — or a hard parse error. Declaring the key makes the authored
+declaration and the enforced behaviour the same fact, which is what ADR-0049
+asks for: it is enforced on arrival, not declared-and-inert.
+
+For authors — including AI authors — the key now appears in the generated
+component reference, and a misspelling (`readOnly`, `read_only`) is a wrong key
+rather than a second de-facto contract the renderer happens to honour.
+
+Purely additive: `readonly` is optional and no default is materialized, so an
+entry that does not author it parses exactly as before, and the bare-string form
+of a highlight field is unchanged.
diff --git a/content/docs/references/ui/component.mdx b/content/docs/references/ui/component.mdx
index df837e7062..d342317cb9 100644
--- a/content/docs/references/ui/component.mdx
+++ b/content/docs/references/ui/component.mdx
@@ -300,7 +300,7 @@ const result = AIChatWindowProps.parse(data);
 
 ## RecordHighlightsField
 
-Highlight field: bare name, or `{name,label?,icon?,type?}`
+Highlight field: bare name, or `{name,label?,icon?,type?,readonly?}`
 
 ### Union Options
 
@@ -322,6 +322,7 @@ Type: `string`
 | **label** | `string` | optional | Display label (overrides schema label) |
 | **icon** | `string` | optional | Icon name (lucide icon key) |
 | **type** | `string` | optional | Override cell renderer type (rare) |
+| **readonly** | `boolean` | optional | Render this chip read-only — suppresses inline editing on the highlight card. Use for hook/automation-maintained columns that must not be hand-edited from the record header. |
 
 ---
 
@@ -334,7 +335,7 @@ Type: `string`
 
 | Property | Type | Required | Description |
 | :--- | :--- | :--- | :--- |
-| **fields** | `string \| { name: string; label?: string; icon?: string; type?: string }[]` | ✅ | Key fields to highlight (1-7 fields max, typically displayed as prominent cards). Each item may be a bare field name or `{name, label?, icon?, type?}` for inline overrides. |
+| **fields** | `string \| { name: string; label?: string; icon?: string; type?: string; … }[]` | ✅ | Key fields to highlight (1-7 fields max, typically displayed as prominent cards). Each item may be a bare field name or `{name, label?, icon?, type?, readonly?}` for inline overrides. |
 | **layout** | `Enum<'horizontal' \| 'vertical'>` | ✅ | Layout orientation for highlight fields |
 | **aria** | `{ ariaLabel?: string; ariaDescribedBy?: string; role?: string }` | optional | ARIA accessibility attributes |
 
diff --git a/packages/spec/src/ui/component.test.ts b/packages/spec/src/ui/component.test.ts
index 2607f37eba..c172e0e8b8 100644
--- a/packages/spec/src/ui/component.test.ts
+++ b/packages/spec/src/ui/component.test.ts
@@ -212,6 +212,47 @@ describe('RecordHighlightsProps', () => {
   it('should reject missing fields', () => {
     expect(() => RecordHighlightsProps.parse({})).toThrow();
   });
+
+  // #5176 — `readonly` is a declared key on the object member of
+  // RecordHighlightsField. objectui's HeaderHighlight gate reads it to keep a
+  // hook-maintained column non-editable; before it was declared the object
+  // member (non-strict) silently stripped it, so the authored intent never
+  // reached the renderer contract at all.
+  it('should preserve an authored readonly on an object-form highlight field', () => {
+    const props = {
+      fields: [{ name: 'supply_share', readonly: true, type: 'number' }],
+    };
+    const result = RecordHighlightsProps.parse(props);
+    const entry = result.fields[0] as { name: string; readonly?: boolean; type?: string };
+    expect(entry.name).toBe('supply_share');
+    expect(entry.type).toBe('number');
+    expect(entry.readonly).toBe(true);
+  });
+
+  it('should preserve readonly: false rather than dropping it', () => {
+    const result = RecordHighlightsProps.parse({ fields: [{ name: 'amount', readonly: false }] });
+    const entry = result.fields[0] as { readonly?: boolean };
+    expect(entry.readonly).toBe(false);
+  });
+
+  it('should leave readonly undefined when it is not authored (no default materialized)', () => {
+    const result = RecordHighlightsProps.parse({ fields: [{ name: 'amount' }] });
+    const entry = result.fields[0] as { readonly?: boolean };
+    expect(entry).not.toHaveProperty('readonly');
+    expect(entry.readonly).toBeUndefined();
+  });
+
+  it('should reject a non-boolean readonly instead of silently stripping it', () => {
+    expect(() => RecordHighlightsProps.parse({ fields: [{ name: 'amount', readonly: 'yes' }] })).toThrow();
+  });
+
+  it('should still accept bare-string and other object-form highlight fields', () => {
+    const result = RecordHighlightsProps.parse({
+      fields: ['name', { name: 'status', label: 'State', icon: 'flag' }],
+    });
+    expect(result.fields[0]).toBe('name');
+    expect(result.fields[1]).toEqual({ name: 'status', label: 'State', icon: 'flag' });
+  });
 });
 
 describe('ComponentPropsMap', () => {
diff --git a/packages/spec/src/ui/component.zod.ts b/packages/spec/src/ui/component.zod.ts
index d07e00fca0..e456af17c1 100644
--- a/packages/spec/src/ui/component.zod.ts
+++ b/packages/spec/src/ui/component.zod.ts
@@ -223,11 +223,18 @@ export const RecordHighlightsField = z.union([
     label: z.string().optional().describe('Display label (overrides schema label)'),
     icon: z.string().optional().describe('Icon name (lucide icon key)'),
     type: z.string().optional().describe('Override cell renderer type (rare)'),
+    // #5176 — declared because it is already enforced: the renderer's
+    // HeaderHighlight gate refuses inline editing on a chip carrying it. Kept
+    // as a declared key (ADR-0049 enforce-or-remove, satisfied on arrival)
+    // rather than an undeclared key the renderer happens to honour — an
+    // undeclared key is silently stripped here, which turns a machine-owned
+    // column editable again with no diagnostic anywhere.
+    readonly: z.boolean().optional().describe('Render this chip read-only — suppresses inline editing on the highlight card. Use for hook/automation-maintained columns that must not be hand-edited from the record header.'),
   }),
-]).describe('Highlight field: bare name, or {name,label?,icon?,type?}');
+]).describe('Highlight field: bare name, or {name,label?,icon?,type?,readonly?}');
 
 export const RecordHighlightsProps = z.object({
-  fields: z.array(RecordHighlightsField).min(1).max(7).describe('Key fields to highlight (1-7 fields max, typically displayed as prominent cards). Each item may be a bare field name or {name, label?, icon?, type?} for inline overrides.'),
+  fields: z.array(RecordHighlightsField).min(1).max(7).describe('Key fields to highlight (1-7 fields max, typically displayed as prominent cards). Each item may be a bare field name or {name, label?, icon?, type?, readonly?} for inline overrides.'),
   layout: z.enum(['horizontal', 'vertical']).default('horizontal').describe('Layout orientation for highlight fields'),
   /** ARIA accessibility */
   aria: AriaPropsSchema.optional().describe('ARIA accessibility attributes'),