@@ -0,0 +1,10 @@
+---
+'@object-ui/plugin-detail': patch
+---
+
+fix(plugin-detail): the discussion header shows no count when a feed read was refused
+
+Clause-②: no
+Metadata-protocol: none
+
+A member who may not read a record's comments saw `Discussion (0)` directly above "You don't have permission to view comments on this record." The timeline's heading counted the rows it holds, and a refused read holds none, so the header claimed the record had no comments when the server only withheld them. When the host reports a refused comment or activity read, the timeline heading now shows its title with no count, and the collapsed discussion toggle reads "Open discussion panel" instead of `Show Discussion (0)`. A readable feed keeps its count, `(0)` included.
@@ -778,9 +778,14 @@ export const RecordActivityTimeline: React.FC<RecordActivityTimelineProps> = ({
           <h2 className="flex items-center gap-2 text-base font-semibold leading-none tracking-tight">
             <Activity className="h-4 w-4" />
             {title}
-            <span className="text-sm font-normal text-muted-foreground">
-              ({filtered.length})
-            </span>
+            {/* A refused read leaves the count unknown, not zero: the rows
+                the reader may not see are not in `filtered`, so a number here
+                would state what the server withheld. */}
+            {!activityDenied && !commentsDenied && (
+              <span className="text-sm font-normal text-muted-foreground" data-testid="activity-count">
+                ({filtered.length})
+              </span>
+            )}
           </h2>
           <div className="flex items-center gap-1">
             {isStream && (
 
@@ -122,6 +122,13 @@ export const RecordChatterPanel: React.FC<RecordChatterPanelProps> = ({
    */
   const feedAria = useRecordAriaProps(config?.feed?.aria);
 
+  // A refused read leaves the count unknown, not zero (see the timeline's
+  // header), so the collapsed toggle names the panel without one.
+  const showLabel =
+    activityDenied || commentsDenied
+      ? t('detail.openDiscussion')
+      : t('detail.showDiscussion', { count: items.length });
+
   const isSidebar = position === 'right' || position === 'left';
   const isInline = position === 'bottom';
 
@@ -218,10 +225,10 @@ export const RecordChatterPanel: React.FC<RecordChatterPanelProps> = ({
           variant="ghost"
           className="w-full justify-start gap-2 text-muted-foreground"
           onClick={() => setCollapsed(false)}
-          aria-label={t('detail.showDiscussion', { count: items.length })}
+          aria-label={showLabel}
         >
           <MessageSquare className="h-4 w-4" />
-          <span>{t('detail.showDiscussion', { count: items.length })}</span>
+          <span>{showLabel}</span>
         </Button>
       ) : (
         <div>
 
@@ -0,0 +1,128 @@
+/**
+ * ObjectUI
+ * Copyright (c) 2024-present ObjectStack Inc.
+ *
+ * The discussion header shows no count when a feed read was refused
+ * (objectstack#27820).
+ *
+ * The timeline's heading drew `(N)` from the rows it holds. A refused comment
+ * read leaves no rows, so a member who may not read the comments saw
+ * `Discussion (0)` right above "You don't have permission to view comments on
+ * this record." — a count the server never gave. The host's refusal signal
+ * (`commentsDenied` / `activityDenied`, the same one that draws the refusal
+ * line) now withholds the count; a readable feed keeps it, `(0)` included.
+ *
+ * Read through the real `en` pack and the `record:chatter` block under a host
+ * `DiscussionContext`, the way the record page mounts it.
+ */
+
+import * as React from 'react';
+import { describe, it, expect, afterEach } from 'vitest';
+import { render, screen, cleanup } from '@testing-library/react';
+import { I18nProvider } from '@object-ui/i18n';
+import { DiscussionContextProvider, RecordContextProvider } from '@object-ui/react';
+import type { FeedItem } from '@object-ui/types';
+import { RecordChatterRenderer } from '../renderers/record-chatter';
+import { RecordChatterPanel } from '../RecordChatterPanel';
+
+const COMMENTS_DENIED = "You don't have permission to view comments on this record.";
+const ACTIVITY_DENIED = "You don't have permission to view activity on this record.";
+
+const comment = (n: number) =>
+  ({
+    id: `c-${n}`,
+    type: 'comment',
+    actor: 'Ada',
+    body: `Comment ${n}`,
+    createdAt: `2026-01-0${n}T00:00:00.000Z`,
+  }) satisfies FeedItem;
+
+type HostItems = React.ComponentProps<typeof DiscussionContextProvider>['items'];
+
+function mountChatter(ctx: { items: HostItems; commentsDenied?: boolean; activityDenied?: boolean }) {
+  return render(
+    <I18nProvider config={{ defaultLanguage: 'en', detectBrowserLanguage: false }}>
+      <RecordContextProvider objectName="crm_account" recordId="rec-1" data={{ id: 'rec-1' }}>
+        <DiscussionContextProvider loading={false} {...ctx}>
+          <RecordChatterRenderer schema={{} as never} />
+        </DiscussionContextProvider>
+      </RecordContextProvider>
+    </I18nProvider>,
+  );
+}
+
+const heading = () => screen.getByRole('heading', { level: 2 });
+
+afterEach(() => cleanup());
+
+describe('the discussion header withholds its count when a feed read was refused (objectstack#27820)', () => {
+  it('a refused comment read: the header shows no count, the refusal line still shows', () => {
+    mountChatter({ items: [], commentsDenied: true });
+
+    expect(heading().textContent?.trim()).toBe('Discussion');
+    expect(heading().textContent).not.toMatch(/\(\d+\)/);
+    expect(screen.queryByTestId('activity-count')).toBeNull();
+    expect(screen.getByTestId('activity-access-denied').textContent).toContain(COMMENTS_DENIED);
+  });
+
+  it('a refused comment read beside readable activity rows still shows no count', () => {
+    const row = {
+      id: 'a-1',
+      type: 'field_change',
+      actor: 'Grace',
+      body: 'Stage moved to qualified',
+      createdAt: '2026-01-02T00:00:00.000Z',
+    } satisfies FeedItem;
+    mountChatter({ items: [row], commentsDenied: true });
+
+    expect(screen.getByText('Stage moved to qualified')).toBeTruthy();
+    expect(heading().textContent).not.toMatch(/\(\d+\)/);
+    expect(screen.getByTestId('activity-access-denied').textContent).toContain(COMMENTS_DENIED);
+  });
+
+  it('a refused activity read shows no count either', () => {
+    mountChatter({ items: [], activityDenied: true });
+
+    expect(heading().textContent).not.toMatch(/\(\d+\)/);
+    expect(screen.getByTestId('activity-access-denied').textContent).toContain(ACTIVITY_DENIED);
+  });
+
+  it('control: a readable record with no comments shows (0)', () => {
+    mountChatter({ items: [] });
+
+    expect(heading()).toHaveTextContent(/^Discussion\s*\(0\)$/);
+    expect(screen.queryByTestId('activity-access-denied')).toBeNull();
+  });
+
+  it('control: a readable record with 3 comments shows (3)', () => {
+    mountChatter({ items: [comment(1), comment(2), comment(3)] });
+
+    expect(heading()).toHaveTextContent(/^Discussion\s*\(3\)$/);
+  });
+});
+
+describe('the collapsed discussion toggle withholds its count the same way (objectstack#27820)', () => {
+  const mountCollapsed = (props: { commentsDenied?: boolean }) =>
+    render(
+      <I18nProvider config={{ defaultLanguage: 'en', detectBrowserLanguage: false }}>
+        <RecordChatterPanel
+          items={[]}
+          config={{ position: 'bottom', collapsible: true, defaultCollapsed: true } as never}
+          {...props}
+        />
+      </I18nProvider>,
+    );
+
+  it('refused: the toggle names the panel without a count', () => {
+    mountCollapsed({ commentsDenied: true });
+
+    const toggle = screen.getByRole('button', { name: 'Open discussion panel' });
+    expect(toggle.textContent).not.toMatch(/\(\d+\)/);
+  });
+
+  it('control: readable, the toggle keeps its (0)', () => {
+    mountCollapsed({});
+
+    expect(screen.getByRole('button', { name: 'Show Discussion (0)' })).toBeTruthy();
+  });
+});