fix: resolve AI response not rendering after long idle/sleep (#129)

* fix: resolve AI response not rendering after long idle/sleep

- Add backgroundThrottling: false to prevent Chromium from throttling
  the renderer process when the window is in the background
- Add powerMonitor.on('resume') to send APP_FOCUS event after system
  wake, triggering DB sync to recover any missed IPC messages
- Re-sync session updates from DB on app focus to capture messages
  lost during sleep/wake or background throttling
- Guard async DB sync with currentSessionIdRef check to prevent
  race condition when user switches sessions during the async call

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: dedupe focus resync logs

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

src/main/index.ts

@@ -8,7 +8,7 @@ import log from './logger'
 
 log.info('Multica starting...')
 
-import { app, shell, BrowserWindow, ipcMain } from 'electron'
+import { app, shell, BrowserWindow, ipcMain, powerMonitor } from 'electron'
 import { join } from 'path'
 import { electronApp, optimizer, is } from '@electron-toolkit/utils'
 import icon from '../../resources/icon.png?asset'
@@ -42,7 +42,8 @@ function createWindow(): BrowserWindow {
       preload: join(__dirname, '../preload/index.js'),
       contextIsolation: true,
       nodeIntegration: false,
-      sandbox: true
+      sandbox: true,
+      backgroundThrottling: false
     }
   })
 
@@ -150,6 +151,13 @@ app.whenReady().then(async () => {
     }
   })
 
+  // Notify renderer when system resumes from sleep (reuse APP_FOCUS to trigger DB sync)
+  powerMonitor.on('resume', () => {
+    if (mainWindow && !mainWindow.isDestroyed()) {
+      mainWindow.webContents.send(IPC_CHANNELS.APP_FOCUS)
+    }
+  })
+
   // Initialize auto-updater
   // Set FORCE_DEV_UPDATE=true to test updates in dev mode
   const forceDevUpdate = process.env.FORCE_DEV_UPDATE === 'true'

src/renderer/src/hooks/useAppSubscriptions.ts

@@ -14,6 +14,7 @@ import { useFileChangeStore } from '../stores/fileChangeStore'
 import { useCommandStore } from '../stores/commandStore'
 import { useAgentStore } from '../stores/agentStore'
 import { toast } from 'sonner'
+import { mergeSessionUpdates } from '../utils/sessionUpdates'
 
 function isGitHeadPath(filePath: string): boolean {
   const normalizedPath = filePath.replace(/\\/g, '/')
@@ -59,6 +60,8 @@ export function useAppSubscriptions(callbacks: SubscriptionCallbacks): void {
 
   // Debounce timer for git branch refresh
   const gitBranchRefreshTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
+  const focusSyncInFlightRef = useRef(false)
+  const lastFocusSyncAtRef = useRef(0)
 
   // Get current session ID for stable reference in effects
   const currentSessionId = currentSession?.id
@@ -232,6 +235,38 @@ export function useAppSubscriptions(callbacks: SubscriptionCallbacks): void {
 
       if (currentSession) {
         await Promise.all([agentRefresh, callbacks.validateCurrentSessionDirectory()])
+
+        // Re-sync session updates from DB to capture any IPC messages that were
+        // lost during system sleep/wake or Chromium background throttling
+        try {
+          const now = Date.now()
+          if (focusSyncInFlightRef.current || now - lastFocusSyncAtRef.current < 500) {
+            if (import.meta.env.DEV) {
+              console.log(
+                '[useAppSubscriptions] Skip focus sync (deduped)',
+                'inFlight:',
+                focusSyncInFlightRef.current,
+                'ageMs:',
+                now - lastFocusSyncAtRef.current
+              )
+            }
+            return
+          }
+          focusSyncInFlightRef.current = true
+          lastFocusSyncAtRef.current = now
+          const sessionId = currentSession.id
+          if (import.meta.env.DEV) {
+            console.log('[useAppSubscriptions] Focus sync start', sessionId)
+          }
+          const freshData = await window.electronAPI.getSession(sessionId)
+          if (freshData?.updates && currentSessionIdRef.current === sessionId) {
+            setSessionUpdates((prev) => mergeSessionUpdates(prev, freshData.updates))
+          }
+        } catch (err) {
+          console.error('[useAppSubscriptions] Failed to refresh session updates on focus:', err)
+        } finally {
+          focusSyncInFlightRef.current = false
+        }
       } else {
         await agentRefresh
       }