perf(sidebar): 消除开关/拖拽的每帧 React 重渲染

- 根因：开关过渡期 ResizeObserver→setCenterRect 每帧重渲染整棵 Sidebar；TabContent 无 memo；内部 Divider/文件树 dock 每 pointermove 全量更新；拖拽残余为 `#root` 每帧 reflow（动画固有成本，A/B 实证非回归）。
- 修复：centerRect 改 ref + 底栏 DOM 直写（零 React 渲染）；TabContent memo（显式比较器，locale/registry/paneId 保持新鲜）；新增 frame-batcher 对 Divider/dock 拖拽按帧合并；拖拽期跳过无意义 locate。
- 验证：单测 76 文件 773 通过；`pnpm test:mount` 12/12（含新 toggle-layout e2e：开关过渡底栏逐帧 0.0px 贴合）；4x CPU 节流 A/B：开关 >17ms 帧 collapse 19→6 / expand 24→4~6，p95 21ms→15ms；拖拽不变（非回归）。
- CR（@codex P1）已修复：`moveTab` 复用同一 tab 对象，比较器改显式比较 `paneId`（含回归单测）。
- 本地 DSH Web 实测通过后按用户要求合入。

fixes #315

src/client/EditorHost.tsx

@@ -31,6 +31,7 @@ import { api, mediaUrl, type SessionScope } from './api.ts'
 import { BinaryDownload } from './binary-download.tsx'
 import { planFirstMatch, planFsReadOutcome, type EditorLoadAction } from './editor-load.ts'
 import { baseName } from './FileTree.tsx'
+import { createFrameBatcher } from './frame-batcher.ts'
 import { openSidebarFile } from './intercept.tsx'
 import { TreePanel } from './TreePanel.tsx'
 import { t } from './locales.ts'
@@ -165,8 +166,16 @@ export function EditorHost(props: {
   // (no window listeners — the captured pointer keeps tracking even off the
   // handle). Local width while dragging, persisted into meta.treeWidth on
   // release. The panel docks right, so dragging LEFT widens it.
+  // Moves are BATCHED per frame (createFrameBatcher): applying every
+  // pointermove is a setState that re-renders this host AND the editor
+  // viewer below it (CodeMirror re-lays out on the width change) at event
+  // cadence — the visible drag lag on slower CPUs (#315). The batch applies
+  // the latest width once per frame; release flushes it and commits.
   const [dragWidth, setDragWidth] = useState<number | null>(null)
   const dragRef = useRef<{ startX: number; startWidth: number } | null>(null)
+  const pendingWidthRef = useRef(0)
+  const dragBatcher = useRef(createFrameBatcher()).current
+  useEffect(() => () => dragBatcher.dispose(), [dragBatcher])
   const treeWidth = dragWidth ?? treeWidthOf(tab)
 
   const onResizeStart = (event: React.PointerEvent): void => {
@@ -178,11 +187,17 @@ export function EditorHost(props: {
   const onResizeMove = (event: React.PointerEvent): void => {
     const drag = dragRef.current
     if (drag === null) return
-    setDragWidth(clampTreeWidth(drag.startWidth + (drag.startX - event.clientX)))
+    pendingWidthRef.current = clampTreeWidth(drag.startWidth + (drag.startX - event.clientX))
+    dragBatcher.schedule(() => setDragWidth(pendingWidthRef.current))
   }
   const onResizeEnd = (event: React.PointerEvent): void => {
     const drag = dragRef.current
     if (drag === null) return
+    // Flush the last pending frame (a release can land with the final move
+    // still queued; without the flush a stray frame would re-apply the
+    // drag width AFTER the null below). Both setStates batch into this same
+    // event, so the committed treeWidth wins visually.
+    dragBatcher.flushNow()
     dragRef.current = null
     setDragWidth(null)
     const finalWidth = clampTreeWidth(drag.startWidth + (drag.startX - event.clientX))

src/client/Sidebar.tsx

@@ -28,7 +28,7 @@
  * drawer floats). Widening does not migrate back: the tabs keep living in
  * the right tree.
  */
-import { createElement, useCallback, useEffect, useMemo, useRef, useState, type DragEvent, type ReactNode } from 'react'
+import { createElement, memo, useCallback, useEffect, useMemo, useRef, useState, type DragEvent, type ReactNode } from 'react'
 import { useSyncExternalStore } from 'react'
 import clsx from 'clsx'
 import { IconCloseFill14, Tooltip } from '@deepseek-ai/dsh-client-ui-primitives'
@@ -52,6 +52,7 @@ import type { TabDragPayload } from './TabBar.tsx'
 import { relativeTo } from './paths.ts'
 import { OrphanedTab } from './OrphanedTab.tsx'
 import { RenderBoundary } from './RenderBoundary.tsx'
+import { tabContentCompare, type TabContentMemoKey } from './tab-content-memo.ts'
 import { detectNewDirectSubagent } from './subagent-detect.ts'
 import { detectNewJob } from './subagent-jobs.ts'
 import { t } from './locales.ts'
@@ -113,23 +114,25 @@ function injectUserCss(attr: string, id: string, cssText: string): HTMLStyleElem
   return tag
 }
 
-/** Render the content of one tab (dispatched by type). */
-function TabContent(props: {
-  tab: SidebarTab
-  sessionId: string
-  cwd: string | undefined
-  expanded: string[]
+/** Props of one tab's content cell = the memo key (tab-content-memo.ts) plus
+ *  the runtime objects/callbacks the cell renders with. The memo comparator
+ *  is the pure `tabContentCompare`; anything in the key decides a re-render
+ *  must propagate, anything outside it must be a stable object (ctx/store)
+ *  or covered by a compared field (paneId covers onOpenDiff's captured
+ *  pane; sessionId/cwd cover onReferenceFile). */
+interface TabContentProps extends TabContentMemoKey {
   onToggleDir: (path: string) => void
   onReferenceFile: (path: string) => void
   ctx: Context
   store: SidebarStore
-  /** Whether this tab is the active one AND the panel is open (live views pause otherwise). */
-  visible: boolean
   /** Fired before a topology node jumps to its child session (see Sidebar). */
   onSubagentJump: (childSessionId: string) => void
   /** Open a diff tab from the git panel (placement handled by the store). */
   onOpenDiff: (tab: SidebarTab) => void
-}) {
+}
+
+/** Render the content of one tab (dispatched by type). */
+const TabContent = memo(function TabContent(props: TabContentProps) {
   const { tab, sessionId, cwd, expanded, onToggleDir, onReferenceFile, ctx, store, visible, onSubagentJump, onOpenDiff } = props
   const scope = { sessionId, cwd }
   const descriptor = ctx.betterSidebar?.getTab(tab.type)
@@ -152,7 +155,7 @@ function TabContent(props: {
       onToggleDir, onReferenceFile, onOpenDiff, onSubagentJump,
     }),
   )
-}
+}, tabContentCompare)
 
 /** The + menu options for the current state, driven by the tab registry.
  * Hidden tabs (editor/diff) never show; `available` returning false shows
@@ -185,6 +188,18 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
   )
   void localeRevision
 
+  // Tab-registry revision: TabContent memo cells must pick up a descriptor
+  // a plugin registers/disposes after mount (the + menu / icons already read
+  // the registry at render). Rare events (plugin (un)mount), so one full
+  // re-render per change is fine — this is what keeps the memoized cells
+  // from going stale, mirroring the localeRevision mechanism above.
+  const [tabsVersion, setTabsVersion] = useState(0)
+  useEffect(() => {
+    const service = ctx.betterSidebar
+    if (service === undefined) return
+    return service.subscribe(() => setTabsVersion(version => version + 1))
+  }, [ctx])
+
   // Narrow (mobile) viewports collapse the two panels into one: the right
   // panel becomes a full-width drawer holding BOTH workbenches, the bottom
   // panel (and its toggle button) disappears, and the layout push is
@@ -497,7 +512,16 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
   // horizontal edges — including the animated margin-right push while the
   // right panel opens/closes; a frame that never appears keeps the initial
   // zero-size fallback (the panel renders at 0 width until measured).
-  const [centerRect, setCenterRect] = useState({ left: 0, right: 0 })
+  // The rect lives in a REF (not state): the open/close transition resizes
+  // the center column EVERY frame for its duration, and reacting per frame
+  // with setState re-renders the whole Sidebar (every mounted tab) at
+  // animation cadence — the visible toggle jank (#315). measureCenter
+  // writes the bottom panel's edges directly (same DOM-write pattern as
+  // applyDrag), so the panel still tracks the column per frame with zero
+  // React work; `centerMeasured` flips ONCE to gate the hidden→visible
+  // first-paint fallback.
+  const centerRectRef = useRef({ left: 0, right: 0 })
+  const [centerMeasured, setCenterMeasured] = useState(false)
   // Refs keep the measure step stable across renders and let it skip work
   // mid-drag: during a width/corner drag the layout push resizes the center
   // column every frame, and reacting (setCenterRect → re-render) would
@@ -518,13 +542,18 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
       return
     }
     const rect = col.getBoundingClientRect()
-    // The bottom panel only cares about the horizontal edges: a pure height
-    // change (the bottom panel itself opening/closing) must not re-render,
-    // so keep the previous object when left/right are unchanged.
-    setCenterRect(prev =>
-      prev.left === rect.left && prev.right === rect.right
-        ? prev
-        : { left: rect.left, right: rect.right })
+    // Ref + direct DOM write (see the centerRectRef comment): the bottom
+    // panel keeps tracking the center column per frame during the right
+    // panel's open/close animation without re-rendering the shell. The
+    // one-shot measured flip renders the panel visible once (a stale
+    // {0,0} fallback would flash full-width).
+    centerRectRef.current = { left: rect.left, right: rect.right }
+    const bottom = bottomRef.current
+    if (bottom !== null) {
+      bottom.style.setProperty('left', `${rect.left}px`)
+      bottom.style.setProperty('right', `${window.innerWidth - rect.right}px`)
+    }
+    setCenterMeasured(prev => (prev ? prev : true))
   }, [])
   useEffect(() => {
     let disposed = false
@@ -571,6 +600,13 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
     let locateFrame: number | null = null
     const scheduleLocate = (): void => {
       if (locateFrame !== null) return
+      // Mid-drag every frame writes --dsh-sidebar-* on <html>'s style
+      // attribute, which is the mutation this watcher observes — relocating
+      // per drag frame is pointless (the center column node cannot change
+      // while the pointer is captured) and adds a querySelector to every
+      // frame's budget (#315). The 1.5s retry below still covers any node
+      // swap that somehow lands mid-drag.
+      if (draggingRef.current) return
       locateFrame = requestAnimationFrame(() => {
         locateFrame = null
         locate()
@@ -708,7 +744,7 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
     // width (innerWidth - state.width - detailsWidth), so this equals
     // `width + detailsWidth` — derived from the measured column, keeping the
     // drag write-only (no React re-render mid-drag).
-    bottomRef.current?.style.setProperty('right', `${(window.innerWidth - centerRect.right) + (width - (state?.width ?? 0))}px`)
+    bottomRef.current?.style.setProperty('right', `${(window.innerWidth - centerRectRef.current.right) + (width - (state?.width ?? 0))}px`)
     writeGeometry(width, height)
   }
 
@@ -1033,6 +1069,7 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
   const renderTab = (tab: SidebarTab, active: boolean, paneId: string, bottom = false) => (
     <TabContent
       tab={tab}
+      paneId={paneId}
       sessionId={sessionId}
       cwd={cwd}
       expanded={state.expanded}
@@ -1043,6 +1080,8 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
       visible={bottom ? state.bottomOpen && active : state.panelOpen && active}
       onSubagentJump={(childSessionId) => { subagentJumpRef.current = childSessionId }}
       onOpenDiff={(diffTab) => { store.reduce(s => openDiffTab(s, paneId, diffTab)) }}
+      localeRevision={localeRevision}
+      tabsVersion={tabsVersion}
     />
   )
 
@@ -1231,7 +1270,7 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
         data-dsh-bottom-panel
         style={{
           height: Math.min(state.bottomHeight, window.innerHeight),
-          left: centerRect.left,
+          left: centerRectRef.current.left,
           // Keep the panel above the on-screen keyboard when the visual
           // viewport shrinks (see the keyboardInset effect).
           bottom: keyboardInset > 0 ? `${keyboardInset}px` : undefined,
@@ -1240,14 +1279,14 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
           // details column's left edge (the details column sits between the
           // center and the right panel, and the right panel's margin-right
           // push is already baked into centerRect.right).
-          right: window.innerWidth - centerRect.right,
+          right: window.innerWidth - centerRectRef.current.right,
           // The seam against the open right panel needs its own hairline
           // (the right panel's border-left alone is covered by this panel's
           // fill — without it the corner looks cut off).
           borderRight: state.panelOpen ? '1px solid var(--dsw-alias-border-l2)' : undefined,
           // Unmeasured center column → keep the panel invisible (zero-size
           // geometry would flash full-width overflow instead).
-          visibility: centerRect.right > 0 ? undefined : 'hidden',
+          visibility: centerMeasured ? undefined : 'hidden',
         }}
        
         data-dragging={(draggingBottom || draggingCorner) || undefined}

src/client/frame-batcher.ts

@@ -0,0 +1,56 @@
+/**
+ * Per-frame task coalescing for pointer-driven interactions.
+ *
+ * Pointer streams fire several times faster than the display refresh, and
+ * applying every event (a React setState, a store reduce) re-renders whole
+ * trees at event cadence — the visible drag lag on slower CPUs (#315). This
+ * batcher keeps the LATEST scheduled task, runs it at most once per
+ * animation frame, and lets the caller flush synchronously on release (so
+ * the final pointer position is never lost to a cancelled frame).
+ *
+ * Callers compose the pending value in a ref before scheduling; the
+ * scheduled task reads that ref, so replacing the task on every event is
+ * cheap (one ref write + one rAF check).
+ */
+export interface FrameBatcher {
+  /** Schedule (or replace) the per-frame task. Safe to call on every event. */
+  schedule(task: () => void): void
+  /** Cancel any pending frame and run the scheduled task synchronously
+   *  (no-op when nothing is scheduled). */
+  flushNow(): void
+  /** Cancel any pending frame and drop the task without running it. */
+  dispose(): void
+}
+
+export function createFrameBatcher(): FrameBatcher {
+  let frame: number | null = null
+  let task: (() => void) | null = null
+
+  const run = (): void => {
+    frame = null
+    const current = task
+    task = null
+    current?.()
+  }
+
+  return {
+    schedule(next) {
+      task = next
+      if (frame === null) frame = requestAnimationFrame(run)
+    },
+    flushNow() {
+      if (frame !== null) {
+        cancelAnimationFrame(frame)
+        frame = null
+      }
+      run()
+    },
+    dispose() {
+      if (frame !== null) {
+        cancelAnimationFrame(frame)
+        frame = null
+      }
+      task = null
+    },
+  }
+}

src/client/split-pane.tsx

@@ -15,6 +15,7 @@ import clsx from 'clsx'
 import type { SidebarState, SidebarTab, SplitNode } from './state.ts'
 import type { DropZone } from './state.ts'
 import { TabBar, type NewTabOption, parseDrag, type TabDragPayload } from './TabBar.tsx'
+import { createFrameBatcher } from './frame-batcher.ts'
 import css from './sidebar.module.css'
 
 /** Actions the workbench needs (bound to the store by the sidebar shell). */
@@ -34,7 +35,18 @@ export interface WorkbenchActions {
  * Deltas are incremental — each move reports the displacement since the
  * previous move — because the store adds every reported delta to the pane
  * sizes; a cumulative (since-pointer-down) delta would be re-added on each
- * move and the divider would run away from the cursor. */
+ * move and the divider would run away from the cursor.
+ *
+ * The moves are BATCHED per frame (createFrameBatcher): a pointer stream
+ * fires faster than the display refresh, and applying each move is a store
+ * reduce that re-renders both workbenches (terminals, editors, trees) per
+ * event — the visible drag lag on slower CPUs (#315). The batch accumulates
+ * the incremental deltas in a ref and applies the summed fraction at most
+ * once per frame; the sum equals what the per-event application would have
+ * produced (the reducer clamps each application, and at a settled position
+ * a clamped sum is clamped to the same boundary), so the result is
+ * indistinguishable at rest and at most one frame behind the cursor.
+ */
 function Divider(props: { dir: 'row' | 'col'; onResize: (deltaFrac: number) => void }) {
   const { dir, onResize } = props
   // `last` is the previous pointer position while dragging; `size` is the
@@ -42,6 +54,9 @@ function Divider(props: { dir: 'row' | 'col'; onResize: (deltaFrac: number) => v
   // normalize the px delta into a fraction.
   const last = useRef({ x: 0, y: 0, size: 0 })
   const [dragging, setDragging] = useState(false)
+  const pendingDelta = useRef(0)
+  const batcher = useRef(createFrameBatcher()).current
+  useEffect(() => () => batcher.dispose(), [batcher])
 
   return (
     <div
@@ -60,12 +75,20 @@ function Divider(props: { dir: 'row' | 'col'; onResize: (deltaFrac: number) => v
       onPointerMove={(event) => {
         if (!event.currentTarget.hasPointerCapture(event.pointerId)) return
         const delta = dir === 'row' ? event.clientX - last.current.x : event.clientY - last.current.y
-        onResize(delta / Math.max(1, last.current.size))
+        pendingDelta.current += delta
+        batcher.schedule(() => {
+          const accumulated = pendingDelta.current
+          pendingDelta.current = 0
+          if (accumulated !== 0) onResize(accumulated / Math.max(1, last.current.size))
+        })
         last.current.x = event.clientX
         last.current.y = event.clientY
       }}
       onPointerUp={(event) => {
         if (!event.currentTarget.hasPointerCapture(event.pointerId)) return
+        // Flush any pending baked delta so the final pointer position lands
+        // (the release event is not a move; dropping it would lose the tail).
+        batcher.flushNow()
         event.currentTarget.releasePointerCapture(event.pointerId)
         setDragging(false)
       }}

src/client/tab-content-memo.ts

@@ -0,0 +1,46 @@
+/**
+ * The memo comparator for one tab's content cell (TabContent in Sidebar.tsx).
+ *
+ * Kept as a pure module so the "what re-renders a tab cell" contract is unit
+ * testable: geometry/store re-renders of the Sidebar shell must NOT reconcile
+ * every mounted tab (xterm/CodeMirror/FileTree subtrees — issue #315), while
+ * locale switches (localeRevision), tab-registry updates (tabsVersion), and
+ * a tab MOVING BETWEEN PANES (paneId — onOpenDiff closes over the pane id,
+ * and moveTab reuses the SAME tab object, so only the pane id identifies the
+ * move) must re-render the cell.
+ */
+import type { SidebarTab } from './state.ts'
+
+/** The fields whose change invalidates a tab cell's memo. Anything a cell's
+ *  render (or its callbacks) depends on must be listed here. */
+export interface TabContentMemoKey {
+  tab: SidebarTab
+  /** The pane this tab currently lives in. onOpenDiff closes over it, and
+   *  moveTab reuses the same tab object when the tab moves panes — without
+   *  comparing paneId the cell would keep the source pane's callback. */
+  paneId: string
+  sessionId: string
+  cwd: string | undefined
+  visible: boolean
+  expanded: string[]
+  localeRevision: string
+  tabsVersion: number
+}
+
+/** True when the cell may skip a re-render (all render-affecting fields
+ *  unchanged). Callback/context identities are deliberately ignored: their
+ *  captured dependencies are stable or covered by the compared fields
+ *  (onReferenceFile → sessionId/cwd, onSubagentJump/onToggleDir → stable
+ *  refs/closures, onOpenDiff → paneId). */
+export function tabContentCompare(prev: TabContentMemoKey, next: TabContentMemoKey): boolean {
+  return (
+    prev.tab === next.tab &&
+    prev.paneId === next.paneId &&
+    prev.sessionId === next.sessionId &&
+    prev.cwd === next.cwd &&
+    prev.visible === next.visible &&
+    prev.expanded === next.expanded &&
+    prev.localeRevision === next.localeRevision &&
+    prev.tabsVersion === next.tabsVersion
+  )
+}