diff --git a/packages/experimental/client-ui-forge/src/client/ChangesTab.module.css b/packages/experimental/client-ui-forge/src/client/ChangesTab.module.css
index 3273865b49..b11b200a18 100644
--- a/packages/experimental/client-ui-forge/src/client/ChangesTab.module.css
+++ b/packages/experimental/client-ui-forge/src/client/ChangesTab.module.css
@@ -318,15 +318,6 @@
   white-space: nowrap;
 }
 
-.fileMessage {
-  display: flex;
-  align-items: center;
-  gap: 10px;
-  margin: 0;
-  padding: 12px 16px;
-  color: var(--dsw-alias-label-secondary);
-}
-
 /* Lines of one file: one column of grid rows, or two cells per row side by side. */
 .code {
   overflow-x: auto;
@@ -433,24 +424,31 @@
 }
 
 /* Collapsed unchanged lines; the row expands them. */
-.gap {
+/* Collapsed unchanged lines, a collapsed large file, and a file whose lines cannot be drawn share one strip;
+   only the first two open on a click. */
+.gap,
+.fileNote {
   display: flex;
   align-items: center;
   gap: 6px;
   box-sizing: border-box;
   width: 100%;
   min-height: 26px;
+  margin: 0;
   padding: 0 12px;
   border: 0;
   background: var(--forge-fill);
   color: var(--dsw-alias-label-tertiary);
-  cursor: pointer;
   font-family: var(--dsw-font-family);
   font-size: 12px;
   line-height: 18px;
   text-align: left;
 }
 
+.gap {
+  cursor: pointer;
+}
+
 .gap:hover:not(:disabled) {
   background: var(--dsw-alias-interactive-bg-hover);
   color: var(--dsw-alias-label-primary);
diff --git a/packages/experimental/client-ui-forge/src/client/DiffFile.tsx b/packages/experimental/client-ui-forge/src/client/DiffFile.tsx
index cd8c91f6d1..da97729464 100644
--- a/packages/experimental/client-ui-forge/src/client/DiffFile.tsx
+++ b/packages/experimental/client-ui-forge/src/client/DiffFile.tsx
@@ -7,7 +7,7 @@
 import { useMemo, useState, type ReactNode } from 'react'
 import clsx from 'clsx'
 import {
-  Button, FileTypeIcon, IconChevronDownOutlineRegular, IconChevronsUpDownOutlineRegular, IconEllipsisOutlineRegular,
+  FileTypeIcon, IconChevronDownOutlineRegular, IconChevronsUpDownOutlineRegular, IconEllipsisOutlineRegular,
   languageForPath, Menu, MenuItemButton, PathLabel, useCodeHighlighter, type CodeHighlighter, type HighlightSpan,
 } from '@deepseek-ai/dsh-client-ui-primitives'
 import type { PropsLocale } from '@deepseek-ai/dsh-client-ui-slots'
@@ -177,15 +177,16 @@ function Lines({ file, text, open, onExpand, split, wrap, t }: Pick<DiffFileProp
 
 function Body(props: DiffFileProps): ReactNode {
   const { file, large, revealed, onReveal, t } = props
-  if (file.binary) return <p className={css.fileMessage}>{t('diff.binary')}</p>
-  if (file.oversized) return <p className={css.fileMessage}>{t('diff.fileTooLarge')}</p>
+  if (file.binary) return <p className={css.fileNote}>{t('diff.binary')}</p>
+  if (file.oversized) return <p className={css.fileNote}>{t('diff.fileTooLarge')}</p>
   if (file.hunks.length === 0) return null
   if (large && !revealed) {
+    // A large file starts as one collapsed strip, drawn and opened like the collapsed unchanged lines.
     return (
-      <div className={css.fileMessage}>
-        <span>{t('diff.oversized')}</span>
-        <Button size="sm" variant="outline" onClick={onReveal}>{t('diff.showAnyway')}</Button>
-      </div>
+      <button type="button" className={css.gap} onClick={onReveal}>
+        <IconChevronsUpDownOutlineRegular size={12} />
+        {t('diff.largeCollapsed', { count: (file.additions + file.deletions).toLocaleString('en-US') })}
+      </button>
     )
   }
   return <Lines {...props} />
diff --git a/packages/experimental/client-ui-forge/src/client/locales.ts b/packages/experimental/client-ui-forge/src/client/locales.ts
index cb923b5c67..6da70da036 100644
--- a/packages/experimental/client-ui-forge/src/client/locales.ts
+++ b/packages/experimental/client-ui-forge/src/client/locales.ts
@@ -117,8 +117,7 @@ export const zh = {
   'diff.badgeUncommitted': '未提交',
   'diff.binary': '二进制文件，无法显示变更',
   'diff.binaryLabel': '二进制',
-  'diff.oversized': '文件较大，默认收起',
-  'diff.showAnyway': '仍然显示',
+  'diff.largeCollapsed': '文件较大，{count} 行变更已收起',
   'diff.fileTooLarge': '文件太大，无法显示变更',
   'diff.error': '无法读取变更',
   'diff.tooLarge': '变更太大，无法在这里显示',
@@ -313,8 +312,7 @@ export const en: Record<ForgePanelKey, string> = {
   'diff.badgeUncommitted': 'Uncommitted',
   'diff.binary': 'Binary file; its changes cannot be shown',
   'diff.binaryLabel': 'Binary',
-  'diff.oversized': 'Large file, collapsed by default',
-  'diff.showAnyway': 'Show anyway',
+  'diff.largeCollapsed': 'Large file: {count} changed lines collapsed',
   'diff.fileTooLarge': 'This file is too large to show',
   'diff.error': 'The changes could not be read',
   'diff.tooLarge': 'These changes are too large to show here',
diff --git a/packages/experimental/client-ui-forge/tests/changes-tab.client.spec.tsx b/packages/experimental/client-ui-forge/tests/changes-tab.client.spec.tsx
index 9db4235c6f..4e5b8036f2 100644
--- a/packages/experimental/client-ui-forge/tests/changes-tab.client.spec.tsx
+++ b/packages/experimental/client-ui-forge/tests/changes-tab.client.spec.tsx
@@ -437,13 +437,12 @@ describe('ChangesTab layout', () => {
     expect(m.section('src/app.ts').querySelector(`.${css.code}`)).not.toBeNull()
 
     const first = m.section('data/huge-1.txt')
-    expect(within(first).getByText(en['diff.oversized'])).toBeTruthy()
-    fireEvent.click(within(first).getByRole('button', { name: en['diff.showAnyway'] }))
+    fireEvent.click(within(first).getByRole('button', { name: 'Large file: 1,001 changed lines collapsed' }))
     // A file with additions only keeps one column in the side-by-side layout.
     expect(first.querySelectorAll('[data-diff-line="add"]')).toHaveLength(1001)
     expect(first.querySelector('[data-diff-pair]')).toBeNull()
     fireEvent.click(within(m.section('data/huge-6.txt')).getByRole('button', { name: 'Expand huge-6.txt' }))
-    expect(within(m.section('data/huge-6.txt')).getByText(en['diff.oversized'])).toBeTruthy()
+    expect(within(m.section('data/huge-6.txt')).getByRole('button', { name: 'Large file: 1,001 changed lines collapsed' })).toBeTruthy()
   })
 
   it('collapses every file from the toolbar while any is expanded, and expands every file once all are collapsed', async () => {