perf(mobile): avoid redundant terminal recovery mounts

src/main/runtime/rpc/terminal-subscribe-blank-mount.test.ts

@@ -27,14 +27,21 @@ describe('terminal.subscribe blank-tab background mount', () => {
   it('requests a renderer tab mount when a mobile subscribe has no headless model', async () => {
     // Why: stale preview text must not hide the missing live model/attachment.
     const cleanups = new Map<string, () => void>()
-    const requestRendererTerminalTabMount = vi.fn()
+    const callOrder: string[] = []
+    const unsubscribeData = vi.fn()
+    const requestRendererTerminalTabMount = vi.fn(() => {
+      callOrder.push('request-mount')
+    })
     const runtime = stubRuntime({
       resolveLeafForHandle: vi.fn().mockReturnValue({ ptyId: 'pty-1' }),
       requestRendererTerminalTabMount,
       hasHeadlessTerminalState: vi.fn().mockReturnValue(false),
       handleMobileSubscribe: vi.fn().mockResolvedValue(true),
       handleMobileUnsubscribe: vi.fn(),
-      subscribeToTerminalData: vi.fn().mockReturnValue(vi.fn()),
+      subscribeToTerminalData: vi.fn(() => {
+        callOrder.push('subscribe-data')
+        return unsubscribeData
+      }),
       readTerminal: vi.fn().mockResolvedValue({ tail: ['stale preview'], truncated: false }),
       serializeTerminalBuffer: vi
         .fn()
@@ -73,9 +80,11 @@ describe('terminal.subscribe blank-tab background mount', () => {
     await vi.waitFor(() =>
       expect(requestRendererTerminalTabMount).toHaveBeenCalledWith('terminal-1')
     )
+    expect(callOrder).toEqual(['subscribe-data', 'request-mount'])
 
     runtime.cleanupSubscription('terminal-1:phone-1')
     await dispatchPromise
+    expect(unsubscribeData).toHaveBeenCalledTimes(1)
   })
 
   it('does not request a renderer tab mount when an attached terminal is legitimately blank', async () => {

src/renderer/src/hooks/useIpcEvents.ts

@@ -15,6 +15,7 @@ import { OPEN_WORKSPACE_BOARD_EVENT } from '@/components/sidebar/useWorkspaceBoa
 import { SPLIT_TERMINAL_PANE_EVENT, CLOSE_TERMINAL_PANE_EVENT } from '@/constants/terminal'
 import { requestBackgroundTerminalWorktreeMount } from '@/components/terminal/background-terminal-worktree-mount'
 import { planMobileTerminalTabMount } from '@/lib/mobile-terminal-tab-mount'
+import { hasRegisteredRuntimeTerminalTab } from '@/runtime/sync-runtime-graph'
 import type { SplitTerminalPaneDetail, CloseTerminalPaneDetail } from '@/constants/terminal'
 import { getVisibleWorktreeIds } from '@/components/sidebar/visible-worktrees'
 import { activateTabNumberShortcut } from '@/lib/tab-number-shortcuts'
@@ -1676,11 +1677,17 @@ export function useIpcEvents(): void {
         }
         // Why: synthetic pty handles need persisted-tab resolution, but a miss
         // must not mount every saved terminal in a large hidden worktree.
-        const mount = planMobileTerminalTabMount(useAppStore.getState(), {
-          worktreeId,
-          ...(tabId ? { tabId } : {}),
-          ...(ptyId ? { ptyId } : {})
-        })
+        const mount = planMobileTerminalTabMount(
+          useAppStore.getState(),
+          {
+            worktreeId,
+            ...(tabId ? { tabId } : {}),
+            ...(ptyId ? { ptyId } : {})
+          },
+          {
+            isTabMounted: hasRegisteredRuntimeTerminalTab
+          }
+        )
         if (mount) {
           requestBackgroundTerminalWorktreeMount(mount)
         }

src/renderer/src/lib/mobile-terminal-tab-mount.test.ts

@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest'
+import { describe, expect, it, vi } from 'vitest'
 import type { AppState } from '@/store/types'
 import { planMobileTerminalTabMount } from './mobile-terminal-tab-mount'
 
@@ -36,4 +36,18 @@ describe('planMobileTerminalTabMount', () => {
       planMobileTerminalTabMount(state(200), { worktreeId: 'wt', ptyId: 'wt@@missing' })
     ).toBeNull()
   })
+
+  it('does not schedule hidden layout work for an already-mounted tab', () => {
+    const isTabMounted = vi.fn().mockReturnValue(true)
+
+    expect(
+      planMobileTerminalTabMount(
+        state(200),
+        { worktreeId: 'wt', ptyId: 'wt@@173' },
+        { isTabMounted }
+      )
+    ).toBeNull()
+    expect(isTabMounted).toHaveBeenCalledTimes(1)
+    expect(isTabMounted).toHaveBeenCalledWith('tab-173')
+  })
 })

src/renderer/src/lib/mobile-terminal-tab-mount.ts

@@ -8,10 +8,15 @@ export type MobileTerminalTabMountRequest = {
   ptyId?: string
 }
 
+type MobileTerminalTabMountOptions = {
+  isTabMounted?: (tabId: string) => boolean
+}
+
 /** Why: exact-tab planning prevents a stale ptyId from mounting every saved xterm (#8597). */
 export function planMobileTerminalTabMount(
   state: Pick<AppState, 'tabsByWorktree' | 'terminalLayoutsByTabId'>,
-  request: MobileTerminalTabMountRequest
+  request: MobileTerminalTabMountRequest,
+  options: MobileTerminalTabMountOptions = {}
 ): BackgroundMountTerminalWorktreeDetail | null {
   if (!request.worktreeId) {
     return null
@@ -19,5 +24,9 @@ export function planMobileTerminalTabMount(
   const tabId =
     request.tabId ??
     (request.ptyId ? resolveTerminalTabIdForPtyId(state, request.worktreeId, request.ptyId) : null)
-  return tabId ? { worktreeId: request.worktreeId, tabIds: [tabId] } : null
+  // Why: replaying the background-mount event for a live pane restarts its
+  // three-second hidden measurement window on every mobile reconnect.
+  return tabId && !options.isTabMounted?.(tabId)
+    ? { worktreeId: request.worktreeId, tabIds: [tabId] }
+    : null
 }