fix(renderer): align native chat pane layering

src/renderer/src/assets/main.css

@@ -400,11 +400,6 @@
   z-index: 40 !important;
 }
 
-/* Above the z-40 updater/onboarding chrome, below the floating workspace panel's z-45. */
-.native-chat-pane-shell:has([data-native-chat-working='true']) {
-  z-index: 44;
-}
-
 [data-sonner-toaster] [data-sonner-toast][data-styled='true'] {
   align-items: flex-start;
   flex-wrap: wrap;

src/renderer/src/components/native-chat/StructuredAgentSessionPaneOverlayLayer.test.tsx

@@ -148,7 +148,7 @@ describe('StructuredAgentSessionPaneOverlayLayer', () => {
     expect(mocks.focusGroup).toHaveBeenCalledWith(WORKTREE_ID, GROUP_ID)
   })
 
-  it('keeps the base z-layer overridable by the working-chat stylesheet rule', () => {
+  it('keeps a working session at the base pane layer', () => {
     const view = render(
       <StructuredAgentSessionPaneOverlayLayer worktreeId={WORKTREE_ID} isWorktreeActive />
     )
@@ -157,7 +157,9 @@ describe('StructuredAgentSessionPaneOverlayLayer', () => {
     )
 
     expect(slot).not.toBeNull()
-    expect(slot?.classList.contains('native-chat-pane-shell')).toBe(true)
+    expect(slot?.hasAttribute('data-retained-pane-host')).toBe(true)
+    expect(slot?.classList.contains('isolate')).toBe(true)
+    expect(slot?.classList.contains('overflow-hidden')).toBe(true)
     expect(slot?.classList.contains('z-10')).toBe(true)
     expect(slot?.style.zIndex).toBe('')
     expect(slot?.querySelector('[data-native-chat-working="true"]')).not.toBeNull()

src/renderer/src/components/native-chat/StructuredAgentSessionPaneOverlayLayer.tsx

@@ -5,7 +5,7 @@ import { isAgentSessionHandleProvider } from '../../../../shared/agent-session-p
 import { useAppStore } from '@/store'
 import { getRuntimeEnvironmentIdForWorktree } from '@/lib/worktree-runtime-owner'
 import { getActiveRuntimeTarget, type RuntimeClientTarget } from '@/runtime/runtime-rpc-client'
-import { tabGroupBodyAnchorName } from '../tab-group/tab-group-body-anchor'
+import { RetainedPaneHost } from '../tab-group/RetainedPaneHost'
 import NativeChatView from './NativeChatView'
 
 type StructuredAgentSessionTab = Tab & {
@@ -29,37 +29,12 @@ const StructuredAgentSessionOverlaySlot = memo(function StructuredAgentSessionOv
   target: RuntimeClientTarget
   onFocusOwningGroup: ((groupId: string) => void) | undefined
 }): React.JSX.Element {
-  const anchorName = groupId !== undefined ? tabGroupBodyAnchorName(groupId) : undefined
-  const style = useMemo<React.CSSProperties>(
-    () =>
-      anchorName
-        ? {
-            position: 'absolute',
-            positionAnchor: anchorName,
-            top: `anchor(${anchorName} top)`,
-            left: `anchor(${anchorName} left)`,
-            width: `anchor-size(${anchorName} width)`,
-            height: `anchor-size(${anchorName} height)`,
-            display: isActive ? 'flex' : 'none',
-            pointerEvents: isActive ? 'auto' : 'none'
-          }
-        : { display: 'none' },
-    [anchorName, isActive]
-  )
-  const focusOwningGroup = useCallback(() => {
-    if (groupId !== undefined && onFocusOwningGroup) {
-      onFocusOwningGroup(groupId)
-    }
-  }, [groupId, onFocusOwningGroup])
-
   return (
-    <div
-      style={style}
-      className="native-chat-pane-shell z-10 min-h-0 min-w-0"
+    <RetainedPaneHost
+      groupId={groupId}
+      isVisible={isActive}
       data-structured-agent-session-overlay-tab-id={tab.id}
-      aria-hidden={!isActive}
-      onPointerDown={focusOwningGroup}
-      onFocusCapture={focusOwningGroup}
+      onFocusOwningGroup={onFocusOwningGroup}
     >
       <NativeChatView
         mode="structured"
@@ -70,7 +45,7 @@ const StructuredAgentSessionOverlaySlot = memo(function StructuredAgentSessionOv
         isVisible={isActive}
         target={target}
       />
-    </div>
+    </RetainedPaneHost>
   )
 })
 

src/renderer/src/components/native-chat/native-chat-stop-layering.test.ts

@@ -6,42 +6,17 @@ function source(path: string): string {
   return readFileSync(join(process.cwd(), path), 'utf8')
 }
 
-function workingChatZIndex(css: string): number {
-  const match =
-    /\.native-chat-pane-shell:has\(\[data-native-chat-working='true'\]\)[^{]*\{[^}]*z-index:\s*(\d+);/s.exec(
-      css
-    )
-  expect(match, 'working native-chat z-index rule not found in main.css').not.toBeNull()
-  return Number(match?.[1])
-}
-
-describe('native chat Stop layering', () => {
-  it('keeps a working chat pane above bottom-right product chrome', () => {
+describe('native chat layering', () => {
+  it('keeps working chat at the pane layer below app notifications and floating surfaces', () => {
     const css = source('src/renderer/src/assets/main.css')
-    const terminalPane = source(
-      'src/renderer/src/components/terminal-pane/TerminalPaneNativeChatPortal.tsx'
-    )
-
-    expect(terminalPane).toContain('native-chat-pane-shell absolute inset-0 z-10')
+    for (const path of [
+      'src/renderer/src/components/terminal-pane/TerminalOverlaySlot.tsx',
+      'src/renderer/src/components/native-chat/StructuredAgentSessionPaneOverlayLayer.tsx'
+    ]) {
+      expect(source(path)).toContain('<RetainedPaneHost')
+    }
+    expect(css).not.toMatch(/\.native-chat-pane-shell:has\(\[data-native-chat-working/)
     expect(css).toMatch(/\[data-sonner-toaster\][^{]*\{[^}]*z-index:\s*40\s*!important;/s)
-    expect(workingChatZIndex(css)).toBeGreaterThan(40)
-  })
-
-  // Why both bounds: raising the working pane over the panel hides a summoned
-  // floating workspace behind the chat column while an agent streams.
-  it('stays under the floating workspace panel while working', () => {
-    // Comments stripped first: the surrounding layering comment cites bare z-40/z-50
-    // tiers, and a reworded one could otherwise be read as the panel's own class.
-    const panel = source(
-      'src/renderer/src/components/floating-terminal/FloatingTerminalPanelSurface.tsx'
-    ).replace(/\/\*[\s\S]*?\*\/|\/\/[^\n]*/g, '')
-    const panelZIndex = Number(
-      /data-floating-terminal-panel[\s\S]*?className=[\s\S]*?z-\[(\d+)\]/.exec(panel)?.[1]
-    )
-
-    // FloatingTerminalPanel.bounds.test.tsx pins this same 45 through a real render.
-    expect(panelZIndex).toBe(45)
-    expect(workingChatZIndex(source('src/renderer/src/assets/main.css'))).toBeLessThan(panelZIndex)
   })
 
   it('publishes working state from both structured and bridge chat roots', () => {

src/renderer/src/components/tab-group/RetainedPaneHost.test.tsx

@@ -0,0 +1,107 @@
+// @vitest-environment happy-dom
+import { act, cleanup, fireEvent, render } from '@testing-library/react'
+import { afterEach, beforeEach, expect, it, vi } from 'vitest'
+import { RetainedPaneHost } from './RetainedPaneHost'
+
+const disconnect = vi.fn()
+let notifyResize: () => void
+let anchors: HTMLDivElement[]
+
+beforeEach(() => {
+  vi.stubGlobal('__ORCA_WEB_CLIENT__', true)
+  vi.stubGlobal(
+    'ResizeObserver',
+    class {
+      constructor(callback: () => void) {
+        notifyResize = callback
+      }
+      observe(): void {}
+      disconnect = disconnect
+    }
+  )
+  disconnect.mockClear()
+  anchors = ['left', 'right'].map((id, index) => {
+    const anchor = document.createElement('div')
+    anchor.dataset.tabGroupBodyId = id
+    anchor.getBoundingClientRect = () => new DOMRect(index * 400, 32, 400, 568)
+    document.body.append(anchor)
+    return anchor
+  })
+})
+
+afterEach(() => {
+  cleanup()
+  anchors.forEach((anchor) => anchor.remove())
+  vi.unstubAllGlobals()
+})
+
+it('retains pane content across group moves and visibility changes using measured browser bounds', () => {
+  const focus = vi.fn()
+  const content = <input defaultValue="draft" />
+  const view = render(
+    <RetainedPaneHost groupId="left" isVisible onFocusOwningGroup={focus}>
+      {content}
+    </RetainedPaneHost>
+  )
+  const host = view.container.firstElementChild as HTMLDivElement
+  const input = view.getByRole('textbox')
+  expect(host.style.top).toBe('32px')
+  expect(host.style.width).toBe('400px')
+  fireEvent.change(input, { target: { value: 'unsent draft' } })
+
+  view.rerender(
+    <RetainedPaneHost groupId="right" isVisible onFocusOwningGroup={focus}>
+      {content}
+    </RetainedPaneHost>
+  )
+  expect(host.style.left).toBe('400px')
+  expect(view.getByRole('textbox')).toBe(input)
+  expect((input as HTMLInputElement).value).toBe('unsent draft')
+  fireEvent.pointerDown(input)
+  expect(focus).toHaveBeenLastCalledWith('right')
+
+  anchors[1].getBoundingClientRect = () => new DOMRect(450, 32, 350, 500)
+  act(() => notifyResize())
+  expect(host.style.left).toBe('450px')
+  expect(host.style.width).toBe('350px')
+
+  view.rerender(
+    <RetainedPaneHost groupId="right" isVisible={false}>
+      {content}
+    </RetainedPaneHost>
+  )
+  expect(host.style.display).toBe('none')
+  expect(host.hasAttribute('inert')).toBe(true)
+  expect(host.contains(input)).toBe(true)
+  view.rerender(
+    <RetainedPaneHost groupId="right" isVisible>
+      {content}
+    </RetainedPaneHost>
+  )
+  expect(host.style.display).toBe('flex')
+  expect(host.hasAttribute('inert')).toBe(false)
+  expect(view.getByRole('textbox')).toBe(input)
+  view.unmount()
+  expect(disconnect).toHaveBeenCalled()
+})
+
+it('allows hidden terminal startup measurement without exposing input or starting fit timers for chat', () => {
+  const timeout = vi.spyOn(window, 'setTimeout')
+  const view = render(
+    <RetainedPaneHost groupId="left" isVisible={false} measureWhileHidden>
+      <input />
+    </RetainedPaneHost>
+  )
+  const host = view.container.firstElementChild as HTMLDivElement
+  expect(host.style.display).toBe('flex')
+  expect(host.style.opacity).toBe('0')
+  expect(host.style.pointerEvents).toBe('none')
+  expect(host.hasAttribute('inert')).toBe(true)
+  view.rerender(
+    <RetainedPaneHost groupId="left" isVisible>
+      <input />
+    </RetainedPaneHost>
+  )
+  expect(timeout).not.toHaveBeenCalled()
+  timeout.mockRestore()
+})

src/renderer/src/components/tab-group/RetainedPaneHost.tsx

@@ -0,0 +1,208 @@
+import { useCallback, useLayoutEffect, useMemo, useRef, useState } from 'react'
+import { SYNC_FIT_PANES_EVENT } from '@/constants/terminal'
+import { tabGroupBodyAnchorName } from './tab-group-body-anchor'
+
+const HAS_CSS_ANCHOR_POSITIONING =
+  typeof CSS !== 'undefined' &&
+  CSS.supports('position-anchor', '--orca-terminal-overlay-probe') &&
+  CSS.supports('top', 'anchor(--orca-terminal-overlay-probe top)') &&
+  CSS.supports('width', 'anchor-size(--orca-terminal-overlay-probe width)')
+const MIN_OVERLAY_FIT_WIDTH_PX = 48
+const MIN_OVERLAY_FIT_HEIGHT_PX = 24
+const FALLBACK_RECT_MIN_CHANGE_PX = 1
+
+function shouldUseCssAnchorPositioning(): boolean {
+  return (
+    HAS_CSS_ANCHOR_POSITIONING &&
+    (globalThis as { __ORCA_WEB_CLIENT__?: boolean }).__ORCA_WEB_CLIENT__ !== true
+  )
+}
+
+type MeasuredFallbackRect = {
+  top: number
+  left: number
+  width: number
+  height: number
+}
+
+type RetainedPaneHostProps = {
+  groupId: string | undefined
+  isVisible: boolean
+  measureWhileHidden?: boolean
+  fitTerminal?: boolean
+  onFocusOwningGroup?: (groupId: string) => void
+  children: React.ReactNode
+  'data-terminal-overlay-tab-id'?: string
+  'data-structured-agent-session-overlay-tab-id'?: string
+}
+
+export function RetainedPaneHost({
+  groupId,
+  isVisible,
+  measureWhileHidden = false,
+  fitTerminal = false,
+  onFocusOwningGroup,
+  children,
+  ...identity
+}: RetainedPaneHostProps): React.JSX.Element {
+  const anchorName = groupId !== undefined ? tabGroupBodyAnchorName(groupId) : undefined
+  const overlayRef = useRef<HTMLDivElement | null>(null)
+  const [measuredFallbackRect, setMeasuredFallbackRect] = useState<MeasuredFallbackRect | null>(
+    null
+  )
+  useLayoutEffect(() => {
+    if (!anchorName || shouldUseCssAnchorPositioning() || !groupId) {
+      return
+    }
+
+    const findBody = (): HTMLElement | null => {
+      for (const candidate of document.querySelectorAll<HTMLElement>('[data-tab-group-body-id]')) {
+        if (candidate.dataset.tabGroupBodyId === groupId) {
+          return candidate
+        }
+      }
+      return null
+    }
+
+    const updateRect = (): void => {
+      const overlay = overlayRef.current
+      const parent = overlay?.parentElement
+      const body = findBody()
+      if (!parent || !body) {
+        setMeasuredFallbackRect(null)
+        return
+      }
+      const parentRect = parent.getBoundingClientRect()
+      const bodyRect = body.getBoundingClientRect()
+      const next: MeasuredFallbackRect = {
+        top: bodyRect.top - parentRect.top,
+        left: bodyRect.left - parentRect.left,
+        width: bodyRect.width,
+        height: bodyRect.height
+      }
+      // Why: ResizeObserver and xterm fit can otherwise amplify sub-pixel jitter forever.
+      setMeasuredFallbackRect((prev) =>
+        prev &&
+        Math.abs(prev.top - next.top) < FALLBACK_RECT_MIN_CHANGE_PX &&
+        Math.abs(prev.left - next.left) < FALLBACK_RECT_MIN_CHANGE_PX &&
+        Math.abs(prev.width - next.width) < FALLBACK_RECT_MIN_CHANGE_PX &&
+        Math.abs(prev.height - next.height) < FALLBACK_RECT_MIN_CHANGE_PX
+          ? prev
+          : next
+      )
+    }
+
+    updateRect()
+    const body = findBody()
+    const parent = overlayRef.current?.parentElement
+    const resizeObserver = new ResizeObserver(updateRect)
+    if (body) {
+      resizeObserver.observe(body)
+    }
+    if (parent) {
+      resizeObserver.observe(parent)
+    }
+    window.addEventListener('resize', updateRect)
+    return () => {
+      resizeObserver.disconnect()
+      window.removeEventListener('resize', updateRect)
+    }
+  }, [anchorName, groupId, isVisible])
+
+  useLayoutEffect(() => {
+    if (!fitTerminal || !isVisible || !anchorName) {
+      return
+    }
+    const dispatchFitIfMeasurable = (): void => {
+      const rect = overlayRef.current?.getBoundingClientRect()
+      if (
+        !rect ||
+        rect.width < MIN_OVERLAY_FIT_WIDTH_PX ||
+        rect.height < MIN_OVERLAY_FIT_HEIGHT_PX
+      ) {
+        return
+      }
+      window.dispatchEvent(new Event(SYNC_FIT_PANES_EVENT))
+    }
+
+    // Why: tab switches can resume visibility before anchor/fallback geometry
+    // settles. Re-fit only after the overlay has real dimensions so the PTY
+    // never stays pinned at a stale ~2-col width.
+    const frameId = requestAnimationFrame(() => {
+      dispatchFitIfMeasurable()
+    })
+    const retryId = window.setTimeout(() => {
+      dispatchFitIfMeasurable()
+    }, 50)
+    const settledRetryId = window.setTimeout(() => {
+      dispatchFitIfMeasurable()
+    }, 150)
+    return () => {
+      cancelAnimationFrame(frameId)
+      window.clearTimeout(retryId)
+      window.clearTimeout(settledRetryId)
+    }
+  }, [anchorName, fitTerminal, isVisible, measuredFallbackRect])
+
+  const style: React.CSSProperties = useMemo(
+    () =>
+      anchorName && shouldUseCssAnchorPositioning()
+        ? {
+            position: 'absolute',
+            positionAnchor: anchorName,
+            top: `anchor(${anchorName} top)`,
+            left: `anchor(${anchorName} left)`,
+            width: `anchor-size(${anchorName} width)`,
+            height: `anchor-size(${anchorName} height)`,
+            display: isVisible || measureWhileHidden ? 'flex' : 'none',
+            opacity: isVisible ? 1 : 0,
+            pointerEvents: isVisible ? 'auto' : 'none'
+          }
+        : anchorName
+          ? {
+              // Why: Chrome builds without CSS anchor positioning otherwise
+              // mount the terminal into a 0x0 overlay. Measure the tab-group
+              // body so the fallback does not cover the tab strip.
+              position: 'absolute',
+              top: measuredFallbackRect?.top ?? 32,
+              left: measuredFallbackRect?.left ?? 0,
+              width: measuredFallbackRect?.width ?? '100%',
+              height: measuredFallbackRect?.height ?? 'calc(100% - 32px)',
+              display: isVisible || measureWhileHidden ? 'flex' : 'none',
+              opacity: isVisible ? 1 : 0,
+              pointerEvents: isVisible ? 'auto' : 'none'
+            }
+          : {
+              position: 'absolute',
+              top: 0,
+              left: 0,
+              width: 0,
+              height: 0,
+              display: 'none',
+              pointerEvents: 'none'
+            },
+    [anchorName, isVisible, measuredFallbackRect, measureWhileHidden]
+  )
+  const focusGroup = useCallback(() => {
+    if (groupId !== undefined && onFocusOwningGroup) {
+      onFocusOwningGroup(groupId)
+    }
+  }, [groupId, onFocusOwningGroup])
+
+  return (
+    <div
+      ref={overlayRef}
+      style={style}
+      // Pane-local layers cannot compete with app notifications or escape their split rectangle.
+      className="isolate z-10 min-h-0 min-w-0 overflow-hidden"
+      data-retained-pane-host=""
+      {...identity}
+      inert={!isVisible}
+      aria-hidden={!isVisible}
+      onPointerDown={focusGroup}
+      onFocusCapture={focusGroup}
+    >
+      {children}
+    </div>
+  )
+}

src/renderer/src/components/terminal-pane/TerminalOverlaySlot.tsx

@@ -1,37 +1,13 @@
-import { memo, useCallback, useLayoutEffect, useMemo, useRef, useState } from 'react'
+import { memo, useLayoutEffect, useState } from 'react'
 import { createPortal } from 'react-dom'
 import { useAppStore } from '../../store'
 import { isProvenProcessExit } from '../../../../shared/terminal-exit-cause'
-import { SYNC_FIT_PANES_EVENT } from '@/constants/terminal'
-import { tabGroupBodyAnchorName } from '../tab-group/tab-group-body-anchor'
+import { RetainedPaneHost } from '../tab-group/RetainedPaneHost'
 import type { ActivityTerminalPortalTarget } from '../activity/activity-terminal-portal'
 import TerminalPane from './TerminalPane'
 import { closeTerminalTab } from '../terminal/terminal-tab-actions'
 import { shouldDeferParkedPtyExitTabClose } from './terminal-parked-tab-watchers'
 
-const HAS_CSS_ANCHOR_POSITIONING =
-  typeof CSS !== 'undefined' &&
-  CSS.supports('position-anchor', '--orca-terminal-overlay-probe') &&
-  CSS.supports('top', 'anchor(--orca-terminal-overlay-probe top)') &&
-  CSS.supports('width', 'anchor-size(--orca-terminal-overlay-probe width)')
-const MIN_OVERLAY_FIT_WIDTH_PX = 48
-const MIN_OVERLAY_FIT_HEIGHT_PX = 24
-const FALLBACK_RECT_MIN_CHANGE_PX = 1
-
-function shouldUseCssAnchorPositioning(): boolean {
-  return (
-    HAS_CSS_ANCHOR_POSITIONING &&
-    (globalThis as { __ORCA_WEB_CLIENT__?: boolean }).__ORCA_WEB_CLIENT__ !== true
-  )
-}
-
-type MeasuredFallbackRect = {
-  top: number
-  left: number
-  width: number
-  height: number
-}
-
 type TerminalOverlaySlotProps = {
   terminalTabId: string
   terminalGeneration: number | undefined
@@ -63,11 +39,6 @@ export const TerminalOverlaySlot = memo(function TerminalOverlaySlot({
   consumeSuppressedPtyExit,
   leaveWorktreeIfEmpty
 }: TerminalOverlaySlotProps): React.JSX.Element {
-  const anchorName = groupId !== undefined ? tabGroupBodyAnchorName(groupId) : undefined
-  const overlayRef = useRef<HTMLDivElement | null>(null)
-  const [measuredFallbackRect, setMeasuredFallbackRect] = useState<MeasuredFallbackRect | null>(
-    null
-  )
   const [shouldMeasureHiddenStartup, setShouldMeasureHiddenStartup] = useState(
     () => useAppStore.getState().pendingStartupByTabId[terminalTabId] !== undefined
   )
@@ -76,144 +47,6 @@ export const TerminalOverlaySlot = memo(function TerminalOverlaySlot({
       setShouldMeasureHiddenStartup(false)
     }
   }, [isVisible, shouldMeasureHiddenStartup])
-  useLayoutEffect(() => {
-    if (!anchorName || shouldUseCssAnchorPositioning() || !groupId) {
-      return
-    }
-
-    const findBody = (): HTMLElement | null => {
-      for (const candidate of document.querySelectorAll<HTMLElement>('[data-tab-group-body-id]')) {
-        if (candidate.dataset.tabGroupBodyId === groupId) {
-          return candidate
-        }
-      }
-      return null
-    }
-
-    const updateRect = (): void => {
-      const overlay = overlayRef.current
-      const parent = overlay?.parentElement
-      const body = findBody()
-      if (!parent || !body) {
-        setMeasuredFallbackRect(null)
-        return
-      }
-      const parentRect = parent.getBoundingClientRect()
-      const bodyRect = body.getBoundingClientRect()
-      const next: MeasuredFallbackRect = {
-        top: bodyRect.top - parentRect.top,
-        left: bodyRect.left - parentRect.left,
-        width: bodyRect.width,
-        height: bodyRect.height
-      }
-      // Why: ResizeObserver and xterm fit can otherwise amplify sub-pixel jitter forever.
-      setMeasuredFallbackRect((prev) =>
-        prev &&
-        Math.abs(prev.top - next.top) < FALLBACK_RECT_MIN_CHANGE_PX &&
-        Math.abs(prev.left - next.left) < FALLBACK_RECT_MIN_CHANGE_PX &&
-        Math.abs(prev.width - next.width) < FALLBACK_RECT_MIN_CHANGE_PX &&
-        Math.abs(prev.height - next.height) < FALLBACK_RECT_MIN_CHANGE_PX
-          ? prev
-          : next
-      )
-    }
-
-    updateRect()
-    const body = findBody()
-    const parent = overlayRef.current?.parentElement
-    const resizeObserver = new ResizeObserver(updateRect)
-    if (body) {
-      resizeObserver.observe(body)
-    }
-    if (parent) {
-      resizeObserver.observe(parent)
-    }
-    window.addEventListener('resize', updateRect)
-    return () => {
-      resizeObserver.disconnect()
-      window.removeEventListener('resize', updateRect)
-    }
-  }, [anchorName, groupId, isVisible])
-
-  useLayoutEffect(() => {
-    if (!isVisible || !anchorName) {
-      return
-    }
-    const dispatchFitIfMeasurable = (): void => {
-      const rect = overlayRef.current?.getBoundingClientRect()
-      if (
-        !rect ||
-        rect.width < MIN_OVERLAY_FIT_WIDTH_PX ||
-        rect.height < MIN_OVERLAY_FIT_HEIGHT_PX
-      ) {
-        return
-      }
-      window.dispatchEvent(new Event(SYNC_FIT_PANES_EVENT))
-    }
-
-    // Why: tab switches can resume visibility before anchor/fallback geometry
-    // settles. Re-fit only after the overlay has real dimensions so the PTY
-    // never stays pinned at a stale ~2-col width.
-    const frameId = requestAnimationFrame(() => {
-      dispatchFitIfMeasurable()
-    })
-    const retryId = window.setTimeout(() => {
-      dispatchFitIfMeasurable()
-    }, 50)
-    const settledRetryId = window.setTimeout(() => {
-      dispatchFitIfMeasurable()
-    }, 150)
-    return () => {
-      cancelAnimationFrame(frameId)
-      window.clearTimeout(retryId)
-      window.clearTimeout(settledRetryId)
-    }
-  }, [anchorName, isVisible, measuredFallbackRect])
-
-  const style: React.CSSProperties = useMemo(
-    () =>
-      anchorName && shouldUseCssAnchorPositioning()
-        ? {
-            position: 'absolute',
-            positionAnchor: anchorName,
-            top: `anchor(${anchorName} top)`,
-            left: `anchor(${anchorName} left)`,
-            width: `anchor-size(${anchorName} width)`,
-            height: `anchor-size(${anchorName} height)`,
-            display: isVisible || shouldMeasureHiddenStartup ? 'flex' : 'none',
-            opacity: isVisible ? 1 : 0,
-            pointerEvents: isVisible ? 'auto' : 'none'
-          }
-        : anchorName
-          ? {
-              // Why: Chrome builds without CSS anchor positioning otherwise
-              // mount the terminal into a 0x0 overlay. Measure the tab-group
-              // body so the fallback does not cover the tab strip.
-              position: 'absolute',
-              top: measuredFallbackRect?.top ?? 32,
-              left: measuredFallbackRect?.left ?? 0,
-              width: measuredFallbackRect?.width ?? '100%',
-              height: measuredFallbackRect?.height ?? 'calc(100% - 32px)',
-              display: isVisible || shouldMeasureHiddenStartup ? 'flex' : 'none',
-              opacity: isVisible ? 1 : 0,
-              pointerEvents: isVisible ? 'auto' : 'none'
-            }
-          : {
-              position: 'absolute',
-              top: 0,
-              left: 0,
-              width: 0,
-              height: 0,
-              display: 'none',
-              pointerEvents: 'none'
-            },
-    [anchorName, isVisible, measuredFallbackRect, shouldMeasureHiddenStartup]
-  )
-  const focusGroup = useCallback(() => {
-    if (groupId !== undefined && onFocusOwningGroup) {
-      onFocusOwningGroup(groupId)
-    }
-  }, [groupId, onFocusOwningGroup])
 
   const terminalPane = (
     <TerminalPane
@@ -267,17 +100,15 @@ export const TerminalOverlaySlot = memo(function TerminalOverlaySlot({
   }
 
   return (
-    <div
-      ref={overlayRef}
-      style={style}
+    <RetainedPaneHost
+      groupId={groupId}
+      isVisible={isVisible}
+      measureWhileHidden={shouldMeasureHiddenStartup}
+      fitTerminal
       data-terminal-overlay-tab-id={terminalTabId}
-      onPointerDown={focusGroup}
-      onFocusCapture={focusGroup}
+      onFocusOwningGroup={onFocusOwningGroup}
     >
       {terminalPane}
-      {/* The chat/terminal toggle now lives in the pane header's action cluster
-          (TerminalPaneHeaderOverlay), beside split/close — not as a separate
-          floating overlay. */}
-    </div>
+    </RetainedPaneHost>
   )
 })

src/renderer/src/components/terminal-pane/TerminalPaneOverlayLayer.react185.test.tsx

@@ -174,7 +174,8 @@ describe('TerminalPaneOverlayLayer fallback measure<->fit loop (React #185)', ()
       capturedResizeCallback?.()
     })
 
-    expect(terminalPaneRenderCount - rendersAfterMount).toBe(1)
+    // Geometry updates belong to the host and do not rerender terminal content.
+    expect(terminalPaneRenderCount - rendersAfterMount).toBe(0)
     expect(overlay?.style.top).toBe('34px')
     expect(overlay?.style.width).toBe('760px')
   })