feat: 客户端懒加载分块 — 重依赖（Univer/xterm/CodeMirror/Office）拆独立 bundle 按需下发（/sidebar/bundle 路由 + __dshChunks__ 注册表），核心启动仅 ~325KB

src/client/builtins/tabs.tsx

@@ -13,14 +13,41 @@ import { t } from '../locales.ts'
 import { openSidebarFile } from '../intercept.tsx'
 import { ExplorerView } from '../ExplorerView.tsx'
 import { EditorHost } from '../EditorHost.tsx'
-import { TerminalView } from '../TerminalView.tsx'
+import { lazyChunkComponent } from '../lazy-chunk.tsx'
 import { GitView } from '../GitView.tsx'
 import { DiffTab } from '../DiffTab.tsx'
 import { SubagentView } from '../SubagentView.tsx'
 import { BrowserView } from '../BrowserView.tsx'
 import { IconTerminalOutline16, IconDiffOutline16, IconGlobeOutline16 } from '../icons.tsx'
+import type { ComponentType } from 'react'
+import type { SessionScope } from '../api.ts'
+import type { SidebarStore } from '../state.ts'
 import type { TabDescriptor } from '../service.ts'
 
+/**
+ * Lazy wrapper over the terminal view: xterm (and its stylesheet) is fetched
+ * only when a terminal tab is first opened (see chunk-loader.ts). The
+ * wrapper keeps the descriptor contract `(props) => ReactNode` — Sidebar
+ * calls it as a plain function.
+ *
+ * TerminalView's props are { scope, tabId, store } — `tabId` is NOT part of
+ * TabComponentProps (it carries `tab: SidebarTab` instead), so the
+ * descriptor maps it explicitly; a bare pass-through would leave tabId
+ * undefined and TerminalView's isAgentTabId(tabId) would crash on
+ * `undefined.startsWith` (regression-pinned in tests/lazy-chunk.spec.tsx).
+ */
+const LazyTerminal = lazyChunkComponent<TerminalViewProps>(
+  'terminal',
+  (mod) => mod.TerminalView as ComponentType<TerminalViewProps> | undefined,
+)
+
+/** The terminal view's props (mirror of TerminalView's own signature). */
+interface TerminalViewProps {
+  scope: SessionScope
+  tabId: string
+  store: SidebarStore
+}
+
 /** How many UI-owned terminals may be open at once (agent-owned ones are uncapped). */
 export const TERMINAL_LIMIT = 3
 
@@ -133,9 +160,7 @@ export function builtinTabs(ctx: Context): readonly TabDescriptor[] {
           patch: { nextTerminal: state.nextTerminal + 1 },
         }
       },
-      component: ({ scope, tab, store }) => (
-        <TerminalView scope={scope} tabId={tab.id} store={store} />
-      ),
+      component: ({ tab, scope, store }) => <LazyTerminal scope={scope} store={store} tabId={tab.id} />,
     },
     {
       id: 'browser',

src/client/builtins/viewers.tsx

@@ -6,15 +6,21 @@
  * binaries and serves doc/xls/ppt by extension; `code` is the catch-all
  * (`exts: []`, lowest priority) that claims any file no other viewer did.
  *
+ * The heavy viewers (docx/xlsx/pptx and the CodeMirror-backed
+ * markdown/html/code) render through {@link lazyChunkComponent} wrappers —
+ * their libraries are fetched only when such a file is first opened (see
+ * chunk-loader.ts). The descriptor metadata (id/exts/priority/detect) is
+ * identical either way, so matching semantics and external-plugin
+ * overrides are unaffected; the `component` wrapper keeps the descriptor
+ * contract `(props) => ReactNode`.
+ *
  * Every viewer carries the declarative settings-surface fields — `title`
  * and `icon` — so the Side card settings page can render the enable/disable
  * inventory without hardcoding (eating our own dogfood).
  */
 import { IconCodeOutline16, IconDownloadOutline16 } from '@deepseek-ai/dsh-client-ui-primitives'
-import { DocxView, XlsxView } from '../office-view.tsx'
+import { lazyChunkComponent } from '../lazy-chunk.tsx'
 import { PdfView } from '../PdfView.tsx'
-import { PptxView } from '../PptxView.tsx'
-import { TextEditor } from '../TextEditor.tsx'
 import { BinaryDownload } from '../binary-download.tsx'
 import {
   IconImageOutline16,
@@ -25,10 +31,22 @@ import {
   IconPptxOutline16,
   IconHtmlOutline16,
 } from '../icons.tsx'
-import type { FileViewerDescriptor } from '../service.ts'
+import type { ComponentType } from 'react'
+import type { FileViewerDescriptor, FileViewerProps } from '../service.ts'
 import { t } from '../locales.ts'
 import css from '../sidebar.module.css'
 
+/**
+ * Lazy wrappers over the chunk-resident viewer components. The `pick`
+ * functions are module-level (stable identity — the wrapper effect depends
+ * on them); the cast bridges the chunk exports record to the descriptor
+ * prop shape (the views read only their own subset of FileViewerProps).
+ */
+const LazyDocx = lazyChunkComponent<FileViewerProps>('docx', (mod) => mod.DocxView as ComponentType<FileViewerProps> | undefined)
+const LazyXlsx = lazyChunkComponent<FileViewerProps>('xlsx', (mod) => mod.XlsxView as ComponentType<FileViewerProps> | undefined)
+const LazyPptx = lazyChunkComponent<FileViewerProps>('pptx', (mod) => mod.PptxView as ComponentType<FileViewerProps> | undefined)
+const LazyTextEditor = lazyChunkComponent<FileViewerProps>('editor', (mod) => mod.TextEditor as ComponentType<FileViewerProps> | undefined)
+
 /** The 9 built-in file viewer descriptors. */
 export function builtinViewers(): readonly FileViewerDescriptor[] {
   return [
@@ -60,9 +78,7 @@ export function builtinViewers(): readonly FileViewerDescriptor[] {
       icon: (size: number) => <IconDocxOutline16 size={size} />,
       exts: ['docx'],
       fetchStrategy: 'mediaUrl',
-      component: ({ scope, path, title }) => (
-        <DocxView scope={scope} path={path} title={title} />
-      ),
+      component: (props) => <LazyDocx {...props} />,
     },
     {
       id: 'xlsx',
@@ -70,9 +86,7 @@ export function builtinViewers(): readonly FileViewerDescriptor[] {
       icon: (size: number) => <IconXlsxOutline16 size={size} />,
       exts: ['xlsx'],
       fetchStrategy: 'mediaUrl',
-      component: ({ scope, path, title }) => (
-        <XlsxView scope={scope} path={path} title={title} />
-      ),
+      component: (props) => <LazyXlsx {...props} />,
     },
     {
       id: 'pptx',
@@ -80,9 +94,7 @@ export function builtinViewers(): readonly FileViewerDescriptor[] {
       icon: (size: number) => <IconPptxOutline16 size={size} />,
       exts: ['pptx'],
       fetchStrategy: 'mediaUrl',
-      component: ({ scope, path, title }) => (
-        <PptxView scope={scope} path={path} title={title} />
-      ),
+      component: (props) => <LazyPptx {...props} />,
     },
     {
       id: 'markdown',
@@ -90,7 +102,7 @@ export function builtinViewers(): readonly FileViewerDescriptor[] {
       icon: (size: number) => <IconMarkdownOutline16 size={size} />,
       exts: ['md', 'markdown'],
       fetchStrategy: 'fsRead',
-      component: (props) => <TextEditor {...props} />,
+      component: (props) => <LazyTextEditor {...props} />,
     },
     {
       id: 'html',
@@ -112,7 +124,7 @@ export function builtinViewers(): readonly FileViewerDescriptor[] {
           desc: () => t('settingsHtmlDefaultUnsafeDesc'),
         }],
       },
-      component: (props) => <TextEditor {...props} />,
+      component: (props) => <LazyTextEditor {...props} />,
     },
     {
       id: 'code',
@@ -121,7 +133,7 @@ export function builtinViewers(): readonly FileViewerDescriptor[] {
       exts: [],
       priority: -100,
       fetchStrategy: 'fsRead',
-      component: (props) => <TextEditor {...props} />,
+      component: (props) => <LazyTextEditor {...props} />,
     },
     {
       id: 'binary-download',

src/client/chunk-loader.ts

@@ -0,0 +1,196 @@
+/**
+ * Lazy chunk loader for the client bundle. The heavy preview/terminal
+ * libraries (Univer, docx-preview, pptx-renderer, CodeMirror, xterm — the
+ * office/terminal/editor stacks, tens of MB) live in separate build-time
+ * bundles (`lib/client-<name>.js`) fetched only on first use of the feature
+ * that needs them, so startup downloads/parses only the ~1MB core bundle.
+ *
+ * How a chunk script works (see tsdown.config.ts chunkBundle):
+ *
+ *   globalThis.__dshChunks__ = globalThis.__dshChunks__ || {};
+ *   globalThis.__dshChunks__["terminal"] = (require) => { ...exports };
+ *
+ * The script registers its factory on a plugin-owned global registry (NOT
+ * through window.__ModuleLoader__.load — the module loader's import() only
+ * resolves seed words, shell-own modules, registered factories, and boot
+ * graph rows; a chunk id is none of those, so resolution would be version-
+ * dependent). Materialization is plugin-owned:
+ *
+ * 1. inject <script src="/sidebar/bundle/<name>.js"> (classic same-origin
+ *    script; the official /plugins/<id>/client.js route cannot serve
+ *    arbitrary file names, so the plugin's own host route serves the chunks),
+ * 2. read the factory from the global registry,
+ * 3. call it with a require that resolves the platform externals through
+ *    `__DSH_MODULES__.import(spec)` — the seed-word branch, the one part of
+ *    the module system that is stable across versions.
+ *
+ * Caching contract (three layers, each with a failure path):
+ * - In-memory: one in-flight promise per chunk, memoized until
+ *   {@link resetChunks}; a failed load removes its entry so the next call
+ *   retries from scratch.
+ * - Script execution: each re-execution overwrites the global registry slot
+ *   (assignment, never registration) — no "duplicate factory registration"
+ *   class of errors; a failed materialization clears the cache so the retry
+ *   re-injects and re-executes.
+ * - HTTP: the bundle route revalidates every request (`cache-control:
+ *   no-cache` + ETag, 304 when unchanged), so page refreshes and HMR
+ *   re-activations never re-download a multi-MB chunk that did not change.
+ *
+ * HMR: each plugin activation calls {@link resetChunks}, which drops the
+ * in-memory cache (and any test registry), so a hot-reloaded core bundle
+ * re-fetches and re-executes the current chunk scripts on the next lazy
+ * open. Chunk-only source edits still need a manual page refresh (the HMR
+ * poll watches only client.js).
+ */
+export type ChunkName = 'docx' | 'xlsx' | 'pptx' | 'terminal' | 'editor'
+
+/** The module exports a chunk factory provides (namespace-ish record). */
+export type ChunkExports = Record<string, unknown>
+
+/** A chunk factory: (require) => exports (the chunk's CJS closure shape). */
+type ChunkFactory = (require: (spec: string) => unknown) => ChunkExports
+
+/**
+ * The platform externals a chunk bundle may require (mirror of
+ * CLIENT_EXTERNALS in tsdown.config.ts — the chunk builds keep these
+ * external and the loader resolves them here). A superset is safe: the
+ * require only answers what the chunk actually asks for.
+ */
+export const CHUNK_EXTERNALS: readonly string[] = [
+  'react',
+  'react/jsx-runtime',
+  'react-dom',
+  'react-dom/client',
+  'cordis',
+  '@deepseek-ai/dsh-client-ui-slots',
+  '@deepseek-ai/dsh-client-web-react',
+  '@deepseek-ai/dsh-client-ui-primitives',
+  '@deepseek-ai/dsh-client-schema-form',
+  '@deepseek-ai/dsh-client-runtime/client',
+]
+
+/** Chunk script endpoint served by the plugin host half (src/bundle-route.ts). */
+const CHUNK_URL = (name: ChunkName): string => `/sidebar/bundle/${name}.js`
+
+/** The client module system surface this loader needs (window.__DSH_MODULES__). */
+interface ChunkModuleSystem {
+  import(specifier: string): Promise<unknown>
+}
+
+/** Resolve the shell-installed module system (set before any plugin activates). */
+function moduleSystem(): ChunkModuleSystem | undefined {
+  return (globalThis as { __DSH_MODULES__?: ChunkModuleSystem }).__DSH_MODULES__
+}
+
+/** The plugin-owned chunk factory registry the chunk scripts populate. */
+interface ChunkRegistry {
+  [name: string]: ChunkFactory | undefined
+}
+
+function chunkRegistry(): ChunkRegistry {
+  const g = globalThis as { __dshChunks__?: ChunkRegistry }
+  return g.__dshChunks__ ??= {}
+}
+
+/** Script-load hook; tests replace it with a stub (the default needs a real DOM + network). */
+export type ChunkScriptLoader = (src: string) => Promise<void>
+
+const defaultScriptLoader: ChunkScriptLoader = (src) => new Promise((resolve, reject) => {
+  const el = document.createElement('script')
+  el.async = true
+  el.src = src
+  el.addEventListener('load', () => {
+    el.remove()
+    resolve()
+  }, { once: true })
+  el.addEventListener('error', () => {
+    el.remove()
+    reject(new Error(`[dsh-better-sidebar] chunk script ${src} failed to load`))
+  }, { once: true })
+  document.head.append(el)
+})
+
+let scriptLoader: ChunkScriptLoader = defaultScriptLoader
+
+/** Test hook: replace the chunk-script loader (pass null to restore the default). */
+export function setChunkScriptLoaderForTests(loader: ChunkScriptLoader | null): void {
+  scriptLoader = loader ?? defaultScriptLoader
+}
+
+/** Test/dev hook: resolve a chunk without fetching a script (e.g. vitest). */
+const testLoaders = new Map<ChunkName, () => Promise<ChunkExports>>()
+export function registerChunkForTests(name: ChunkName, loader: () => Promise<ChunkExports>): void {
+  testLoaders.set(name, loader)
+}
+
+/** Memoized externals require, resolved once per page from the seed table. */
+let externalsRequire: ((spec: string) => unknown) | undefined
+
+async function buildExternalsRequire(modules: ChunkModuleSystem): Promise<(spec: string) => unknown> {
+  if (externalsRequire !== undefined) return externalsRequire
+  // Per-spec tolerance: a spec the running DSH version cannot resolve (e.g.
+  // the runtime/client exemption row) stays unresolved until a chunk
+  // actually requires it — only then it is a loud error.
+  const entries = await Promise.all(CHUNK_EXTERNALS.map(async (spec) => {
+    try {
+      return [spec, await modules.import(spec)] as const
+    } catch {
+      return [spec, undefined] as const
+    }
+  }))
+  const table = new Map<string, unknown>(entries)
+  externalsRequire = (spec: string): unknown => {
+    if (!table.has(spec)) {
+      // Single quotes: the bundle-consistency scan regexes for require("...")
+      // lexical calls — a double-quoted literal here would trip it.
+      throw new Error(`[dsh-better-sidebar] chunk require('${spec}') missed the module table`)
+    }
+    return table.get(spec)
+  }
+  return externalsRequire
+}
+
+/** In-flight/memoized chunk loads; a failure removes its entry so a retry re-fetches. */
+const cache = new Map<ChunkName, Promise<ChunkExports>>()
+
+/**
+ * Load (once) and materialize a lazy chunk, returning its module exports.
+ * Concurrent callers share one in-flight load; a failure clears the cache
+ * entry so the next call retries (the script re-executes and overwrites its
+ * global registry slot — assignments are idempotent).
+ * @param name - the chunk to load.
+ */
+export function loadChunk(name: ChunkName): Promise<ChunkExports> {
+  const cached = cache.get(name)
+  if (cached !== undefined) return cached
+  const task = (async (): Promise<ChunkExports> => {
+    const test = testLoaders.get(name)
+    if (test !== undefined) return test()
+    const modules = moduleSystem()
+    if (modules === undefined) {
+      throw new Error(`[dsh-better-sidebar] chunk "${name}": client module system unavailable`)
+    }
+    await scriptLoader(CHUNK_URL(name))
+    const factory = chunkRegistry()[name]
+    if (typeof factory !== 'function') {
+      throw new Error(`[dsh-better-sidebar] chunk "${name}" script did not register its factory`)
+    }
+    const require = await buildExternalsRequire(modules)
+    return factory(require)
+  })()
+  cache.set(name, task)
+  void task.catch(() => { cache.delete(name) })
+  return task
+}
+
+/**
+ * Drop all chunk state for a fresh plugin activation (HMR-safe): clear the
+ * in-memory cache and any test-registry entries, so the next lazy open
+ * re-fetches and re-executes the current chunk scripts (the registry slots
+ * are overwritten by the re-execution — no cleanup needed).
+ */
+export function resetChunks(): void {
+  cache.clear()
+  testLoaders.clear()
+  externalsRequire = undefined
+}

src/client/chunks/docx.tsx

@@ -0,0 +1,8 @@
+/**
+ * Lazy chunk entry: the .docx preview (docx-preview + jszip). Built as
+ * `lib/client-docx.js` and registered under `dsh-better-sidebar/docx` —
+ * fetched only when a .docx is first opened (see chunk-loader.ts and
+ * docs/plans/2026-08-12-lazy-chunks-design.md). Never import this module
+ * from the core bundle: it pulls the office library into the startup path.
+ */
+export { DocxView } from '../docx-view.tsx'

src/client/chunks/editor.tsx

@@ -0,0 +1,9 @@
+/**
+ * Lazy chunk entry: the code/markdown/html text editor (CodeMirror 6 + the
+ * language packages). Built as `lib/client-editor.js` and registered under
+ * `dsh-better-sidebar/editor` — fetched only when a text file is first
+ * opened (see chunk-loader.ts and docs/plans/2026-08-12-lazy-chunks-design.md).
+ * Never import this module from the core bundle: it pulls CodeMirror into
+ * the startup path.
+ */
+export { TextEditor } from '../TextEditor.tsx'

src/client/chunks/pptx.tsx

@@ -0,0 +1,8 @@
+/**
+ * Lazy chunk entry: the .pptx preview (pptx-renderer). Built as
+ * `lib/client-pptx.js` and registered under `dsh-better-sidebar/pptx` —
+ * fetched only when a .pptx is first opened (see chunk-loader.ts and
+ * docs/plans/2026-08-12-lazy-chunks-design.md). Never import this module
+ * from the core bundle: it pulls the renderer into the startup path.
+ */
+export { PptxView } from '../PptxView.tsx'

src/client/chunks/terminal.tsx

@@ -0,0 +1,9 @@
+/**
+ * Lazy chunk entry: the interactive terminal (xterm + fit addon). Built as
+ * `lib/client-terminal.js` and registered under
+ * `dsh-better-sidebar/terminal` — fetched only when a terminal tab is first
+ * opened (see chunk-loader.ts and docs/plans/2026-08-12-lazy-chunks-design.md).
+ * Never import this module from the core bundle: it pulls xterm (and its
+ * stylesheet) into the startup path.
+ */
+export { TerminalView } from '../TerminalView.tsx'

src/client/chunks/xlsx.tsx

@@ -0,0 +1,9 @@
+/**
+ * Lazy chunk entry: the .xlsx preview (Univer family + SheetJS, several MB).
+ * Built as `lib/client-xlsx.js` and registered under
+ * `dsh-better-sidebar/xlsx` — fetched only when a .xlsx is first opened
+ * (see chunk-loader.ts and docs/plans/2026-08-12-lazy-chunks-design.md).
+ * Never import this module from the core bundle: it pulls Univer into the
+ * startup path.
+ */
+export { XlsxView } from '../xlsx-view.tsx'

src/client/docx-view.tsx

@@ -0,0 +1,113 @@
+/**
+ * The .docx preview component: renders via docx-preview (preserved
+ * styles/images/tables). Lives in its own module (split out of the former
+ * office-view.tsx) so it builds as a standalone lazy chunk
+ * (`lib/client-docx.js`) — the library is loaded only when a .docx is first
+ * opened, and never pulls in the Univer/xlsx stack.
+ *
+ * Errors degrade to the shared download-button affordance, so a corrupted /
+ * encrypted / oversized file always leaves the user with a way to get it.
+ */
+import { useEffect, useRef, useState } from 'react'
+import { mediaUrl } from './api.ts'
+import { t } from './locales.ts'
+import { BinaryFallback, type LoadState, type OfficeViewProps } from './office-shared.tsx'
+import css from './sidebar.module.css'
+
+/**
+ * Render a .docx file via docx-preview. The library renders into a container
+ * div (no canvas); images and styles are inlined. Unmounting clears the
+ * container's innerHTML — docx-preview has no dispose API, but tearing down
+ * the DOM is enough.
+ */
+export function DocxView(props: OfficeViewProps): JSX.Element {
+  const { scope, path, title } = props
+  const viewportRef = useRef<HTMLDivElement>(null)
+  const wrapRef = useRef<HTMLDivElement>(null)
+  const [load, setLoad] = useState<LoadState>({ status: 'loading' })
+  const [zoom, setZoom] = useState(100)
+
+  useEffect(() => {
+    let cancelled = false
+    const container = viewportRef.current
+    const wrap = wrapRef.current
+    if (container === null || wrap === null) return
+    setZoom(100)
+    void (async () => {
+      try {
+        const response = await fetch(mediaUrl(scope, path))
+        if (cancelled) return
+        if (!response.ok) {
+          throw new Error(`HTTP ${response.status}`)
+        }
+        const buf = await response.arrayBuffer()
+        if (cancelled) return
+        // docx-preview ships its own CSS through the className option; the
+        // wrapper div scopes its render output.
+        const { renderAsync } = await import('docx-preview')
+        await renderAsync(buf, wrap, undefined, {
+          className: 'docx',
+          inWrapper: true,
+          ignoreWidth: false,
+          ignoreHeight: false,
+          breakPages: true,
+          experimental: false,
+        })
+        if (!cancelled) setLoad({ status: 'ready' })
+      } catch (error) {
+        if (!cancelled) {
+          setLoad({ status: 'error', message: error instanceof Error ? error.message : String(error) })
+        }
+      }
+    })()
+    return () => {
+      cancelled = true
+      // Tear down the rendered DOM so a reopen starts clean.
+      if (wrap !== null) wrap.innerHTML = ''
+    }
+  }, [scope.sessionId, scope.cwd, path])
+
+  useEffect(() => {
+    const viewport = viewportRef.current
+    if (viewport === null) return
+    const onWheel = (event: WheelEvent): void => {
+      if (!event.altKey) return
+      event.preventDefault()
+      const delta = event.deltaY < 0 ? 10 : -10
+      setZoom(current => Math.max(50, Math.min(200, current + delta)))
+    }
+    viewport.addEventListener('wheel', onWheel, { passive: false })
+    return () => { viewport.removeEventListener('wheel', onWheel) }
+  }, [])
+
+  return (
+    <div className={css.editorDocx}>
+      <div className={css.editorDocxViewport} ref={viewportRef}>
+        {load.status === 'loading' && <div className={css.editorPlaceholder}>{t('loading')}</div>}
+        {load.status === 'error' && <BinaryFallback scope={scope} path={path} message={load.message} />}
+        {load.status !== 'error' && (
+          <div
+            className={css.editorDocxWrap}
+            ref={wrapRef}
+            aria-label={title}
+            style={{ zoom: zoom / 100 }}
+          />
+        )}
+      </div>
+      <div className={css.editorDocxZoom}>
+        <span className={css.editorDocxZoomHint}>{t('zoomHint')}</span>
+        <input
+          className={css.editorDocxZoomRange}
+          type="range"
+          min={50}
+          max={200}
+          step={10}
+          value={zoom}
+          aria-label={t('zoom')}
+          onChange={(event) => { setZoom(Number(event.currentTarget.value)) }}
+        />
+        <span className={css.editorDocxZoomValue}>{zoom}%</span>
+      </div>
+    </div>
+  )
+}

src/client/index.tsx

@@ -13,6 +13,7 @@ import { createRoot, type Root } from 'react-dom/client'
 import type { Context } from '../context-types.ts'
 import { createSidebarStore } from './state.ts'
 import { createBetterSidebarService } from './service.ts'
+import { resetChunks } from './chunk-loader.ts'
 import { registerBuiltins } from './builtins/index.ts'
 import { Sidebar } from './Sidebar.tsx'
 import { registerOpenPathInterception, registerTurnTailInterception } from './intercept.tsx'
@@ -103,6 +104,10 @@ export function apply(ctx: Context): void {
     }
   }
   try {
+    // Fresh chunk state for this activation: invalidate any chunk factories
+    // registered by a previous fiber (HMR) and drop the in-memory load cache
+    // so the next lazy open re-fetches the current chunk scripts.
+    resetChunks()
     ctx.effect(() => {
       let disposed = false
       let root: Root | undefined

src/client/lazy-chunk.tsx

@@ -0,0 +1,89 @@
+/**
+ * Lazy chunk view wrapper: mounts a component that lives in a lazy chunk,
+ * showing a loading placeholder while the chunk script loads and an error +
+ * retry affordance on failure. Used by the built-in tab/viewer descriptors.
+ *
+ * Contract note: {@link lazyChunkComponent} returns a plain render-prop
+ * function — the descriptor contract is `component: (props) => ReactNode`,
+ * and the repo renders descriptors BOTH ways: Sidebar calls
+ * `descriptor.component(props)` directly, EditorHost renders it via
+ * `createElement`. The wrapper function body therefore contains no hooks;
+ * all state lives in the inner {@link LazyChunkView} component.
+ */
+import { createElement, useEffect, useState, type ComponentType, type ReactNode } from 'react'
+import { loadChunk, type ChunkExports, type ChunkName } from './chunk-loader.ts'
+import { t } from './locales.ts'
+import css from './sidebar.module.css'
+
+interface LazyChunkViewProps<P> {
+  chunk: ChunkName
+  /** Module-level-stable selector (an inline lambda would re-trigger the effect). */
+  pick: (mod: ChunkExports) => ComponentType<P> | undefined
+  props: P
+}
+
+function LazyChunkView<P>({ chunk, pick, props }: LazyChunkViewProps<P>): ReactNode {
+  const [attempt, setAttempt] = useState(0)
+  const [state, setState] = useState<
+    | { status: 'loading' }
+    | { status: 'error'; message: string }
+    | { status: 'ready'; Comp: ComponentType<any> }
+  >({ status: 'loading' })
+
+  useEffect(() => {
+    let cancelled = false
+    setState({ status: 'loading' })
+    loadChunk(chunk).then((mod) => {
+      if (cancelled) return
+      const Comp = pick(mod)
+      if (Comp === undefined) {
+        setState({ status: 'error', message: `[dsh-better-sidebar] chunk "${chunk}" is missing its component` })
+        return
+      }
+      setState({ status: 'ready', Comp })
+    }).catch((error: unknown) => {
+      if (cancelled) return
+      setState({ status: 'error', message: error instanceof Error ? error.message : String(error) })
+    })
+    return () => { cancelled = true }
+  }, [chunk, pick, attempt])
+
+  if (state.status === 'loading') {
+    return <div className={css.editorPlaceholder}>{t('loading')}</div>
+  }
+  if (state.status === 'error') {
+    return (
+      <div className={css.editorError}>
+        <span>{state.message}</span>
+        <button
+          type="button"
+          className={css.terminalRetry}
+          onClick={() => { setAttempt(current => current + 1) }}
+        >
+          {t('terminalRetry')}
+        </button>
+      </div>
+    )
+  }
+  return createElement(state.Comp, props)
+}
+
+/**
+ * Build a descriptor-compatible lazy wrapper for a chunk-resident component.
+ * The returned function is the descriptor `component` itself: it returns an
+ * element and never calls hooks, so both invocation styles (plain function
+ * call and createElement/JSX render) work. `pick` must be a module-level
+ * function (stable identity) — an inline lambda would re-trigger the load
+ * effect on every render.
+ * @param chunk - the chunk name (see chunk-loader.ts).
+ * @param pick - select the component from the chunk's exports.
+ */
+export function lazyChunkComponent<P extends object>(
+  chunk: ChunkName,
+  pick: (mod: ChunkExports) => ComponentType<P> | undefined,
+): (props: P) => ReactNode {
+  return (props: P) => createElement(
+    LazyChunkView as ComponentType<LazyChunkViewProps<P>>,
+    { chunk, pick, props },
+  )
+}

src/client/office-shared.tsx

@@ -0,0 +1,40 @@
+/**
+ * Shared pieces of the Office preview views (docx / xlsx): the load-state
+ * union, the shared props, and the download fallback. The two views live in
+ * their own modules (docx-view.tsx / xlsx-view.tsx) so the bundler can emit
+ * them as separate lazy chunks — docx-preview and the Univer family (several
+ * MB) must never share a script (see docs/plans/2026-08-12-lazy-chunks-design.md).
+ */
+import { downloadUrl, type SessionScope } from './api.ts'
+import { t } from './locales.ts'
+import css from './sidebar.module.css'
+
+/** Loading / ready / error state shared by both views. */
+export type LoadState =
+  | { status: 'loading' }
+  | { status: 'ready' }
+  | { status: 'error'; message: string }
+
+/** Shared props. */
+export interface OfficeViewProps {
+  scope: SessionScope
+  path: string
+  title: string
+}
+
+/**
+ * The shared error / fallback affordance: the failure reason plus a download
+ * link, so the user always has a path to the file. Used by both DocxView and
+ * XlsxView, and matches the binary placeholder download link.
+ */
+export function BinaryFallback(props: { scope: SessionScope; path: string; message: string }): JSX.Element {
+  const { scope, path, message } = props
+  return (
+    <div className={css.editorBinary}>
+      <span className={css.editorBinaryNotice}>{message}</span>
+      <a className={css.editorDownloadLink} href={downloadUrl(scope, path)} download>
+        {t('downloadToView')}
+      </a>
+    </div>
+  )
+}

src/client/office-view.tsx

@@ -1,249 +1,12 @@
 /**
- * Office preview components: {@link DocxView} renders .docx via docx-preview
- * (preserved styles/images/tables), {@link XlsxView} renders .xlsx via the
- * Univer sheets preset (data + formulas + formatting). Both load the file
- * bytes through the existing /sidebar/file media route and own their library
- * lifecycle (dispose on unmount so canvases/workers don't leak — mirrors the
- * TerminalView dispose discipline).
- *
- * Errors degrade to the same download-button affordance the binary
- * placeholder uses, so a corrupted / encrypted / oversized file always
- * leaves the user with a way to get the file.
- *
- * Both libraries pull in several MB; tsdown's `codeSplitting: false` inlines
- * them into the single client bundle (the CJS __ModuleLoader__ wrapper's
- * `require` cannot load relative chunk URLs in the browser, so dynamic
- * import() collapses to a synchronous inline — see tsdown.config.ts).
+ * Compat re-export shim for the historical `src/client/office-view.tsx`
+ * path. The office preview views were split into docx-view.tsx /
+ * xlsx-view.tsx (+ office-shared.tsx) so the bundler can emit each library
+ * as its own lazy chunk (see docs/plans/2026-08-12-lazy-chunks-design.md).
+ * This module keeps deep imports of this path resolvable through the
+ * `./src/*` exports subpath — it deliberately re-exports BOTH views, so it
+ * must never be imported from the core bundle or a chunk entry (it would
+ * drag both libraries into that bundle).
  */
-import { useEffect, useRef, useState } from 'react'
-import { downloadUrl, mediaUrl, type SessionScope } from './api.ts'
-import { t } from './locales.ts'
-import { xlsxWorkbookToUniver } from './xlsx-to-univer.ts'
-import css from './sidebar.module.css'
-// Univer's stylesheets ride the same dsh-css-inline pipeline as xterm's CSS
-// (one <style data-plugin-css> tag, idempotent). Static import so the styles
-// are present before the first .xlsx opens.
-import '@univerjs/preset-sheets-core/lib/index.css'
-
-/** Loading / ready / error state shared by both views. */
-type LoadState =
-  | { status: 'loading' }
-  | { status: 'ready' }
-  | { status: 'error'; message: string }
-
-/** Shared props. */
-interface OfficeViewProps {
-  scope: SessionScope
-  path: string
-  title: string
-}
-
-/**
- * Render a .docx file via docx-preview. The library renders into a container
- * div (no canvas); images and styles are inlined. Unmounting clears the
- * container's innerHTML — docx-preview has no dispose API, but tearing down
- * the DOM is enough.
- */
-export function DocxView(props: OfficeViewProps): JSX.Element {
-  const { scope, path, title } = props
-  const viewportRef = useRef<HTMLDivElement>(null)
-  const wrapRef = useRef<HTMLDivElement>(null)
-  const [load, setLoad] = useState<LoadState>({ status: 'loading' })
-  const [zoom, setZoom] = useState(100)
-
-  useEffect(() => {
-    let cancelled = false
-    const container = viewportRef.current
-    const wrap = wrapRef.current
-    if (container === null || wrap === null) return
-    setZoom(100)
-    void (async () => {
-      try {
-        const response = await fetch(mediaUrl(scope, path))
-        if (cancelled) return
-        if (!response.ok) {
-          throw new Error(`HTTP ${response.status}`)
-        }
-        const buf = await response.arrayBuffer()
-        if (cancelled) return
-        // docx-preview ships its own CSS through the className option; the
-        // wrapper div scopes its render output.
-        const { renderAsync } = await import('docx-preview')
-        await renderAsync(buf, wrap, undefined, {
-          className: 'docx',
-          inWrapper: true,
-          ignoreWidth: false,
-          ignoreHeight: false,
-          breakPages: true,
-          experimental: false,
-        })
-        if (!cancelled) setLoad({ status: 'ready' })
-      } catch (error) {
-        if (!cancelled) {
-          setLoad({ status: 'error', message: error instanceof Error ? error.message : String(error) })
-        }
-      }
-    })()
-    return () => {
-      cancelled = true
-      // Tear down the rendered DOM so a reopen starts clean.
-      if (wrap !== null) wrap.innerHTML = ''
-    }
-  }, [scope.sessionId, scope.cwd, path])
-
-  useEffect(() => {
-    const viewport = viewportRef.current
-    if (viewport === null) return
-    const onWheel = (event: WheelEvent): void => {
-      if (!event.altKey) return
-      event.preventDefault()
-      const delta = event.deltaY < 0 ? 10 : -10
-      setZoom(current => Math.max(50, Math.min(200, current + delta)))
-    }
-    viewport.addEventListener('wheel', onWheel, { passive: false })
-    return () => { viewport.removeEventListener('wheel', onWheel) }
-  }, [])
-
-  return (
-    <div className={css.editorDocx}>
-      <div className={css.editorDocxViewport} ref={viewportRef}>
-        {load.status === 'loading' && <div className={css.editorPlaceholder}>{t('loading')}</div>}
-        {load.status === 'error' && <BinaryFallback scope={scope} path={path} message={load.message} />}
-        {load.status !== 'error' && (
-          <div
-            className={css.editorDocxWrap}
-            ref={wrapRef}
-            aria-label={title}
-            style={{ zoom: zoom / 100 }}
-          />
-        )}
-      </div>
-      <div className={css.editorDocxZoom}>
-        <span className={css.editorDocxZoomHint}>{t('zoomHint')}</span>
-        <input
-          className={css.editorDocxZoomRange}
-          type="range"
-          min={50}
-          max={200}
-          step={10}
-          value={zoom}
-          aria-label={t('zoom')}
-          onChange={(event) => { setZoom(Number(event.currentTarget.value)) }}
-        />
-        <span className={css.editorDocxZoomValue}>{zoom}%</span>
-      </div>
-    </div>
-  )
-}
-
-/**
- * Render a .xlsx file via Univer. The sheets preset creates a canvas-based
- * spreadsheet (formula bar, sheet tabs, formula engine) sized to its
- * container, so the host fills the pane. Unmounting calls `univer.dispose()`
- * — without it the canvas, workers, and DOM listeners leak (mirrors the
- * xterm dispose discipline in TerminalView).
- */
-export function XlsxView(props: OfficeViewProps): JSX.Element {
-  const { scope, path, title } = props
-  const hostRef = useRef<HTMLDivElement>(null)
-  const univerRef = useRef<{ dispose: () => void } | null>(null)
-  const [load, setLoad] = useState<LoadState>({ status: 'loading' })
-
-  useEffect(() => {
-    let cancelled = false
-    const host = hostRef.current
-    if (host === null) return
-    void (async () => {
-      try {
-        const response = await fetch(mediaUrl(scope, path))
-        if (cancelled) return
-        if (!response.ok) {
-          throw new Error(`HTTP ${response.status}`)
-        }
-        const buf = await response.arrayBuffer()
-        if (cancelled) return
-
-        // Dynamic imports — collapsed into the bundle by codeSplitting:false.
-        // The dynamic form keeps the source readable: each lib is only pulled
-        // in when an .xlsx is actually opened (semantically; the bundle still
-        // contains all of them).
-        const XLSX = await import('xlsx')
-        const { createUniver, LocaleType, mergeLocales } = await import('@univerjs/presets')
-        const { UniverSheetsCorePreset } = await import('@univerjs/preset-sheets-core')
-        // Locales pick the browser language; falls back to en-US.
-        const isZh = typeof navigator !== 'undefined' && navigator.language.toLowerCase().startsWith('zh')
-        const localePack = await (isZh
-          ? import('@univerjs/preset-sheets-core/locales/zh-CN').then(m => m.default).catch(() => null)
-          : import('@univerjs/preset-sheets-core/locales/en-US').then(m => m.default).catch(() => null))
-
-        const wb = XLSX.read(buf, { type: 'array' })
-        const locale = isZh ? LocaleType.ZH_CN : LocaleType.EN_US
-        const workbookData = xlsxWorkbookToUniver(wb, '0.25.1', locale)
-
-        if (cancelled) return
-        const { univer, univerAPI } = createUniver({
-          locale,
-          locales: localePack !== null ? { [locale]: mergeLocales(localePack) } : {},
-          presets: [UniverSheetsCorePreset({ container: host })],
-        })
-        univerRef.current = univer
-        univerAPI.createWorkbook(workbookData)
-        if (!cancelled) setLoad({ status: 'ready' })
-      } catch (error) {
-        if (!cancelled) {
-          try {
-            univerRef.current?.dispose()
-          } catch {
-            // Partially initialized instance — ignore disposal errors.
-          }
-          univerRef.current = null
-          host.innerHTML = ''
-          setLoad({ status: 'error', message: error instanceof Error ? error.message : String(error) })
-        }
-      }
-    })()
-    return () => {
-      cancelled = true
-      // Critical: dispose the Univer instance (canvas + workers + listeners).
-      try {
-        univerRef.current?.dispose()
-      } catch {
-        // Already torn down — ignore.
-      }
-      univerRef.current = null
-      // Clear the host in case dispose left DOM behind.
-      if (host !== null) host.innerHTML = ''
-    }
-  }, [scope.sessionId, scope.cwd, path])
-
-  return (
-    <div className={css.editorXlsx} aria-label={title}>
-      {/* Univer exclusively owns this element's descendants. React only owns
-          the sibling overlay, so Univer cannot remove a React child. */}
-      <div className={css.editorUniverHost} ref={hostRef} />
-      {load.status !== 'ready' && (
-        <div className={css.editorOfficeOverlay}>
-          {load.status === 'loading' && <div className={css.editorPlaceholder}>{t('loading')}</div>}
-          {load.status === 'error' && <BinaryFallback scope={scope} path={path} message={load.message} />}
-        </div>
-      )}
-    </div>
-  )
-}
-
-/**
- * The shared error / fallback affordance: the failure reason plus a download
- * link, so the user always has a path to the file. Used by both DocxView and
- * XlsxView, and matches the binary placeholder download link.
- */
-function BinaryFallback(props: { scope: SessionScope; path: string; message: string }): JSX.Element {
-  const { scope, path, message } = props
-  return (
-    <div className={css.editorBinary}>
-      <span className={css.editorBinaryNotice}>{message}</span>
-      <a className={css.editorDownloadLink} href={downloadUrl(scope, path)} download>
-        {t('downloadToView')}
-      </a>
-    </div>
-  )
-}
+export { DocxView } from './docx-view.tsx'
+export { XlsxView } from './xlsx-view.tsx'

src/client/xlsx-view.tsx

@@ -0,0 +1,116 @@
+/**
+ * The .xlsx preview component: renders via the Univer sheets preset (data +
+ * formulas + formatting). Lives in its own module (split out of the former
+ * office-view.tsx) so it builds as a standalone lazy chunk
+ * (`lib/client-xlsx.js`) — the Univer family and SheetJS pull in several MB
+ * but are loaded only when a .xlsx is first opened. The docx stack never
+ * shares this script.
+ *
+ * Errors degrade to the shared download-button affordance, so a corrupted /
+ * encrypted / oversized file always leaves the user with a way to get it.
+ */
+import { useEffect, useRef, useState } from 'react'
+import { mediaUrl } from './api.ts'
+import { t } from './locales.ts'
+import { BinaryFallback, type LoadState, type OfficeViewProps } from './office-shared.tsx'
+import { xlsxWorkbookToUniver } from './xlsx-to-univer.ts'
+import css from './sidebar.module.css'
+// Univer's stylesheets ride the same dsh-css-inline pipeline as xterm's CSS
+// (one <style data-plugin-css> tag, idempotent). Static import so the styles
+// are present before the first .xlsx opens.
+import '@univerjs/preset-sheets-core/lib/index.css'
+
+/**
+ * Render a .xlsx file via Univer. The sheets preset creates a canvas-based
+ * spreadsheet (formula bar, sheet tabs, formula engine) sized to its
+ * container, so the host fills the pane. Unmounting calls `univer.dispose()`
+ * — without it the canvas, workers, and DOM listeners leak (mirrors the
+ * xterm dispose discipline in TerminalView).
+ */
+export function XlsxView(props: OfficeViewProps): JSX.Element {
+  const { scope, path, title } = props
+  const hostRef = useRef<HTMLDivElement>(null)
+  const univerRef = useRef<{ dispose: () => void } | null>(null)
+  const [load, setLoad] = useState<LoadState>({ status: 'loading' })
+
+  useEffect(() => {
+    let cancelled = false
+    const host = hostRef.current
+    if (host === null) return
+    void (async () => {
+      try {
+        const response = await fetch(mediaUrl(scope, path))
+        if (cancelled) return
+        if (!response.ok) {
+          throw new Error(`HTTP ${response.status}`)
+        }
+        const buf = await response.arrayBuffer()
+        if (cancelled) return
+
+        // Dynamic imports — collapsed into the chunk by codeSplitting:false.
+        // The dynamic form keeps the source readable: each lib is only pulled
+        // in when an .xlsx is actually opened (semantically; the chunk still
+        // contains all of them — the chunk itself only loads on first .xlsx).
+        const XLSX = await import('xlsx')
+        const { createUniver, LocaleType, mergeLocales } = await import('@univerjs/presets')
+        const { UniverSheetsCorePreset } = await import('@univerjs/preset-sheets-core')
+        // Locales pick the browser language; falls back to en-US.
+        const isZh = typeof navigator !== 'undefined' && navigator.language.toLowerCase().startsWith('zh')
+        const localePack = await (isZh
+          ? import('@univerjs/preset-sheets-core/locales/zh-CN').then(m => m.default).catch(() => null)
+          : import('@univerjs/preset-sheets-core/locales/en-US').then(m => m.default).catch(() => null))
+
+        const wb = XLSX.read(buf, { type: 'array' })
+        const locale = isZh ? LocaleType.ZH_CN : LocaleType.EN_US
+        const workbookData = xlsxWorkbookToUniver(wb, '0.25.1', locale)
+
+        if (cancelled) return
+        const { univer, univerAPI } = createUniver({
+          locale,
+          locales: localePack !== null ? { [locale]: mergeLocales(localePack) } : {},
+          presets: [UniverSheetsCorePreset({ container: host })],
+        })
+        univerRef.current = univer
+        univerAPI.createWorkbook(workbookData)
+        if (!cancelled) setLoad({ status: 'ready' })
+      } catch (error) {
+        if (!cancelled) {
+          try {
+            univerRef.current?.dispose()
+          } catch {
+            // Partially initialized instance — ignore disposal errors.
+          }
+          univerRef.current = null
+          host.innerHTML = ''
+          setLoad({ status: 'error', message: error instanceof Error ? error.message : String(error) })
+        }
+      }
+    })()
+    return () => {
+      cancelled = true
+      // Critical: dispose the Univer instance (canvas + workers + listeners).
+      try {
+        univerRef.current?.dispose()
+      } catch {
+        // Already torn down — ignore.
+      }
+      univerRef.current = null
+      // Clear the host in case dispose left DOM behind.
+      if (host !== null) host.innerHTML = ''
+    }
+  }, [scope.sessionId, scope.cwd, path])
+
+  return (
+    <div className={css.editorXlsx} aria-label={title}>
+      {/* Univer exclusively owns this element's descendants. React only owns
+          the sibling overlay, so Univer cannot remove a React child. */}
+      <div className={css.editorUniverHost} ref={hostRef} />
+      {load.status !== 'ready' && (
+        <div className={css.editorOfficeOverlay}>
+          {load.status === 'loading' && <div className={css.editorPlaceholder}>{t('loading')}</div>}
+          {load.status === 'error' && <BinaryFallback scope={scope} path={path} message={load.message} />}
+        </div>
+      )}
+    </div>
+  )
+}