diff --git a/.gitignore b/.gitignore
index 37e0c34..d57d635 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@
 node_modules
 dist/
 *.local
+*.tsbuildinfo
 
 # mimosa 扫描钩子的本地缓存（scripts/hooks 写入，不入库）
 .mimosa
diff --git a/src/previewfit.ts b/src/previewfit.ts
new file mode 100644
index 0000000..ba975f5
--- /dev/null
+++ b/src/previewfit.ts
@@ -0,0 +1,50 @@
+// docx 分页纸面按预览栏宽度等比缩小。只缩不放：栏宽够放下整页时保持 100%。
+// gutter 与 styles.css 里 .docx-wrapper 的左右 padding（12px + 12px）对齐。
+
+export function computeFitScale(containerWidth: number, pageWidth: number, gutter: number): number {
+  if (!Number.isFinite(containerWidth) || !Number.isFinite(pageWidth) || pageWidth <= 0) return 1
+  if (!Number.isFinite(gutter)) return 1
+  const available = containerWidth - gutter
+  if (!(available > 0)) return 1
+  return Math.min(1, available / pageWidth)
+}
+
+const PAGE_GUTTER_PX = 24
+
+/** host 是 docx-preview 的渲染根（内含 .docx-wrapper）；el 是用来量栏宽的元素。
+ *  拖动分隔条时 el 变宽，ResizeObserver 重算。返回的函数卸下监听并清掉行内缩放。 */
+export function fitPagesToWidth(host: HTMLElement, el: HTMLElement): () => void {
+  const apply = () => {
+    const wrapper = host.querySelector<HTMLElement>('.docx-wrapper')
+    const page = host.querySelector<HTMLElement>('section.docx')
+    if (!wrapper || !page) return
+    const scale = computeFitScale(el.clientWidth, page.offsetWidth, PAGE_GUTTER_PX)
+    wrapper.style.transformOrigin = 'top left'
+    wrapper.style.transform = scale < 1 ? `scale(${scale})` : ''
+    const nextHeight = `${Math.round(wrapper.offsetHeight * scale)}px`
+    if (host.style.height !== nextHeight) host.style.height = nextHeight
+    host.style.overflow = 'hidden'
+    host.style.minHeight = '0'
+  }
+  apply()
+  if (typeof ResizeObserver === 'undefined') {
+    return () => clearFit(host)
+  }
+  const observer = new ResizeObserver(() => apply())
+  observer.observe(el)
+  return () => {
+    observer.disconnect()
+    clearFit(host)
+  }
+}
+
+function clearFit(host: HTMLElement) {
+  const wrapper = host.querySelector<HTMLElement>('.docx-wrapper')
+  if (wrapper) {
+    wrapper.style.transform = ''
+    wrapper.style.transformOrigin = ''
+  }
+  host.style.height = ''
+  host.style.overflow = ''
+  host.style.minHeight = ''
+}
diff --git a/src/previewsetup.ts b/src/previewsetup.ts
index bf2e268..9c7595f 100644
--- a/src/previewsetup.ts
+++ b/src/previewsetup.ts
@@ -4,6 +4,7 @@
 import { configureFilePreviewLoaders, configureLinkPreviewFetcher, renderMarkdown, setSafeHTML, stripUnsafeLinks } from '@ui'
 import { auth } from './auth'
 import type { LinkPreviewData } from '@ui'
+import { fitPagesToWidth } from './previewfit'
 
 const fetchBuf = async (url: string | undefined): Promise<ArrayBuffer> => {
   const r = await fetch(url!)
@@ -43,7 +44,7 @@ const docxLoader = async (el: HTMLElement, source: { contentUrl?: string; name?:
     el.innerHTML = ''
     await renderAsync(buf, el, el, { className: 'docx', inWrapper: true, breakPages: true })
     stripUnsafeLinks(el)
-    return
+    return fitPagesToWidth(el, el)
   } catch (err) {
     console.error('[preview:docx] page render failed, falling back', source.name, err)
   }
diff --git a/src/styles.css b/src/styles.css
index 04b2012..3016203 100644
--- a/src/styles.css
+++ b/src/styles.css
@@ -203,8 +203,8 @@ button { font-family: inherit; font-size: inherit; color: inherit; }
 .preview-pane-body { flex: 1; min-height: 0; overflow: auto; }
 .preview-pane-body .ui-fp { height: 100%; }
 .preview-pane-body .ui-fp-pdf { height: 100%; min-height: 480px; border: none; }
-.docx-wrapper { background: var(--bg-inset) !important; padding: 12px; }
-.docx-wrapper > section.docx { background: var(--bg) !important; color: var(--text); box-shadow: var(--shadow-md); }
+.docx-wrapper { background: var(--bg-inset) !important; padding: 12px; display: flex; flex-direction: column; align-items: flex-start !important; }
+.docx-wrapper > section.docx { background: var(--paper) !important; color: var(--paper-ink); box-shadow: var(--shadow-md); }
 /* 过程段内联组（流式/关闭自动折叠时，按原位渲染的过程容器） */
 .part-group { margin: 2px 0; }
 
diff --git a/test/previewfit.test.ts b/test/previewfit.test.ts
new file mode 100644
index 0000000..31a9806
--- /dev/null
+++ b/test/previewfit.test.ts
@@ -0,0 +1,21 @@
+import { describe, it, expect } from 'vitest'
+import { computeFitScale } from '../src/previewfit'
+
+describe('computeFitScale', () => {
+  it('keeps the page at 100% when the column is wider than the page', () => {
+    expect(computeFitScale(1100, 794, 24)).toBe(1)
+    expect(computeFitScale(818, 794, 24)).toBe(1)
+  })
+
+  it('scales the page down to the column width after subtracting the gutter', () => {
+    expect(computeFitScale(420, 794, 24)).toBeCloseTo((420 - 24) / 794)
+    expect(computeFitScale(794, 794, 24)).toBeCloseTo((794 - 24) / 794)
+  })
+
+  it('does not invert or zoom when the width is unusable', () => {
+    expect(computeFitScale(0, 794, 24)).toBe(1)
+    expect(computeFitScale(20, 794, 24)).toBe(1)
+    expect(computeFitScale(420, 0, 24)).toBe(1)
+    expect(computeFitScale(Number.NaN, 794, 24)).toBe(1)
+  })
+})
diff --git a/tsconfig.tsbuildinfo b/tsconfig.tsbuildinfo
deleted file mode 100644
index e2a2ab1..0000000
--- a/tsconfig.tsbuildinfo
+++ /dev/null
@@ -1 +0,0 @@
-{"root":["./src/App.tsx","./src/api.ts","./src/auth.ts","./src/contracts.ts","./src/live.ts","./src/main.tsx","./src/messageparts.ts","./src/outbox.ts","./src/passwords.ts","./src/pluginHost.ts","./src/previewsetup.ts","./src/previewtabs.ts","./src/projectmeta.ts","./src/runstate.test.ts","./src/runstate.ts","./src/scrollsync.ts","./src/store.ts","./src/tasklist.ts","./src/theme.ts","./src/toolkind.ts","./src/workspaces.ts","./src/components/AdminUsersModal.tsx","./src/components/AdminZone.tsx","./src/components/AgentTracker.tsx","./src/components/ArtifactsPanel.tsx","./src/components/BorrowPanels.tsx","./src/components/Conversation.tsx","./src/components/DocViewer.tsx","./src/components/LoginPage.tsx","./src/components/PreviewPane.tsx","./src/components/ProcessTimeline.tsx","./src/components/ProjectSettingsModal.tsx","./src/components/SettingsModal.tsx","./src/components/TaskSidebar.tsx","./src/components/TopBar.tsx","./src/components/Workbench.tsx","./src/components/Workspaces.tsx","./src/components/adminSections.tsx","./test/auth.test.ts","./test/contracts.test.ts","./test/design-guard.test.ts","./test/html-sinks.test.ts","./test/live.test.ts","./test/messageparts.test.ts","./test/notice.test.ts","./test/outbox.test.ts","./test/previewtabs.test.ts","./test/scrollsync.test.ts","./test/send.test.ts","./test/tasklist.test.ts","./test/theme.test.ts","./test/toolkind.test.ts","./test/workspaces.test.ts"],"version":"5.9.3"}
\ No newline at end of file