diff --git a/src/renderer/src/components/Terminal.tsx b/src/renderer/src/components/Terminal.tsx
index 4189b0e44a1..010eb226a63 100644
--- a/src/renderer/src/components/Terminal.tsx
+++ b/src/renderer/src/components/Terminal.tsx
@@ -2674,11 +2674,10 @@ const WorktreeSplitSurface = React.memo(function WorktreeSplitSurface({
         backgroundMountTabIds={backgroundMountTabIds}
         activationDeferredMountTabIds={activationDeferredMountTabIds}
       />
+      {/* Why: always mounted — its slots host persistent <webview> guests that die if the slot leaves the DOM (STA-3228); hidden worktrees park the pane subtree, so targeted background mounts only pay for empty slot divs. */}
+      <BrowserPaneOverlayLayer worktreeId={worktreeId} isWorktreeActive={isVisible} />
       {isVisible || backgroundMountTabIds === null ? (
-        <>
-          <BrowserPaneOverlayLayer worktreeId={worktreeId} isWorktreeActive={isVisible} />
-          <EmulatorPaneOverlayLayer worktreeId={worktreeId} isWorktreeActive={isVisible} />
-        </>
+        <EmulatorPaneOverlayLayer worktreeId={worktreeId} isWorktreeActive={isVisible} />
       ) : null}
       <AiVaultSessionDropLayer worktreeId={worktreeId} enabled={isVisible} />
     </div>
diff --git a/src/renderer/src/components/browser-pane/browser-page-viewport.test.ts b/src/renderer/src/components/browser-pane/browser-page-viewport.test.ts
index 9172ddae7f2..c4df770d2eb 100644
--- a/src/renderer/src/components/browser-pane/browser-page-viewport.test.ts
+++ b/src/renderer/src/components/browser-pane/browser-page-viewport.test.ts
@@ -46,6 +46,41 @@ describe('ensureBrowserPageViewport', () => {
   it('returns null until the slot viewport root is registered', () => {
     expect(ensureBrowserPageViewport('page-1', 'workspace-missing')).toBeNull()
   })
+
+  it('reuses the cached viewport while the slot root is unchanged', () => {
+    mountSlotViewport('workspace-1')
+    const first = ensureBrowserPageViewport('page-1', 'workspace-1')
+    const second = ensureBrowserPageViewport('page-1', 'workspace-1')
+
+    expect(second).toBe(first)
+  })
+
+  it('keeps the parked viewport while the slot root is unregistered', () => {
+    const root = mountSlotViewport('workspace-1')
+    const parked = ensureBrowserPageViewport('page-1', 'workspace-1')
+    root.remove()
+    registerBrowserOverlaySlotViewport('workspace-1', null)
+
+    expect(ensureBrowserPageViewport('page-1', 'workspace-1')).toBe(parked)
+  })
+
+  it('rebuilds under a replacement slot root instead of returning the stranded shell (STA-3228)', () => {
+    const oldRoot = mountSlotViewport('workspace-1')
+    const stale = ensureBrowserPageViewport('page-1', 'workspace-1')!
+    // Worktree overlay unmounts while hidden: slot root leaves the DOM with the shell inside.
+    oldRoot.remove()
+    registerBrowserOverlaySlotViewport('workspace-1', null)
+    const newRoot = mountSlotViewport('workspace-1')
+
+    const rebuilt = ensureBrowserPageViewport('page-1', 'workspace-1')
+
+    expect(rebuilt).not.toBeNull()
+    expect(rebuilt).not.toBe(stale)
+    expect(rebuilt!.shell.parentElement).toBe(newRoot)
+    expect(rebuilt!.shell.isConnected).toBe(true)
+    expect(stale.shell.isConnected).toBe(false)
+    expect(getBrowserPageViewportContainer('page-1')).toBe(rebuilt!.container)
+  })
 })
 
 describe('syncBrowserPageChromeInset', () => {
diff --git a/src/renderer/src/components/browser-pane/browser-page-viewport.ts b/src/renderer/src/components/browser-pane/browser-page-viewport.ts
index f6cae76105a..d0d1ed7bc8d 100644
--- a/src/renderer/src/components/browser-pane/browser-page-viewport.ts
+++ b/src/renderer/src/components/browser-pane/browser-page-viewport.ts
@@ -65,11 +65,18 @@ export function ensureBrowserPageViewport(
   browserPageId: string,
   workspaceTabId: string
 ): BrowserPageViewport | null {
+  const root = slotViewportRoots.get(workspaceTabId)
   const existing = browserPageViewports.get(browserPageId)
   if (existing) {
-    return existing
+    if (!root || existing.shell.parentElement === root) {
+      return existing
+    }
+    // Why: a remounted slot root (overlay unmount while hidden, cross-worktree tab move) strands
+    // the cached shell in a removed subtree where its guest is already dead; drop it so the caller
+    // rebuilds against the live root instead of rendering into detached DOM forever (STA-3228).
+    existing.shell.remove()
+    browserPageViewports.delete(browserPageId)
   }
-  const root = slotViewportRoots.get(workspaceTabId)
   if (!root) {
     return null
   }