feat(expo): 后台超过 5 分钟才断开会话 WebSocket

- 进入 background 后延迟释放长连，回到前台则取消计时；短切应用保持连接
- 池支持 subscribeConversationPoolSlotDisposed；聊天页在槽位释放时同步状态
- 前台 active 时按需 connect 或重绑会话
- backgroundDisconnectAfterMs 默认 300_000（5 分钟）

未纳入：api/uploads/ 本地文件

Co-authored-by: Cursor <cursoragent@cursor.com>

app-expo/src/core/config.ts

@@ -21,5 +21,10 @@ export const config = {
     reconnectBaseDelayMs: 1_000,
     reconnectMaxDelayMs: 30_000,
     heartbeatIntervalMs: 30_000,
+    /**
+     * 仅当 App 处于 `background` 连续超过该毫秒数才释放当前会话 WebSocket。
+     * 短暂切到其它应用再返回时保持连接，避免反复重连。
+     */
+    backgroundDisconnectAfterMs: 300_000,
   },
 } as const;

app-expo/src/features/conversation/conversation-ws-background-pool.ts

@@ -1,6 +1,8 @@
 import type { QueryClient } from '@tanstack/react-query';
 import { AppState, type AppStateStatus } from 'react-native';
 
+import { config } from '@/core/config';
+
 import {
   RealtimeSession,
   type RealtimeSessionUiOwner,
@@ -10,23 +12,67 @@ type Slot = { conversationId: string; session: RealtimeSession };
 
 let slot: Slot | null = null;
 
-/** 与常见聊天 App 一致：仅当应用进入 background 时断开长连（避免后台挂 socket）；inactive 不处理以减少控制中心等短暂打断 */
+/** 回到前台时取消；超时触发才真正 dispose，避免短切换也断连 */
+let backgroundDisconnectTimer: ReturnType<typeof setTimeout> | null = null;
+
+const slotDisposedListeners = new Set<() => void>();
+
+/** 槽位被释放（超时 / 登出 / 换会话等）时通知；用于聊天页同步 sessionRef 与连接状态 */
+export function subscribeConversationPoolSlotDisposed(
+  cb: () => void,
+): () => void {
+  slotDisposedListeners.add(cb);
+  return () => {
+    slotDisposedListeners.delete(cb);
+  };
+}
+
+/** 与常见聊天 App 一致：后台停留超过 `backgroundDisconnectAfterMs` 再断开长连；短切应用保持 socket */
 let backgroundUnsubscribe: (() => void) | null = null;
 
+function cancelBackgroundDisconnectTimer(): void {
+  if (backgroundDisconnectTimer != null) {
+    clearTimeout(backgroundDisconnectTimer);
+    backgroundDisconnectTimer = null;
+  }
+}
+
+function scheduleBackgroundDisconnect(): void {
+  cancelBackgroundDisconnectTimer();
+  backgroundDisconnectTimer = setTimeout(() => {
+    backgroundDisconnectTimer = null;
+    disposeSlot();
+  }, config.ws.backgroundDisconnectAfterMs);
+}
+
 function installBackgroundLifecycleOnce(): void {
   if (backgroundUnsubscribe) return;
   const sub = AppState.addEventListener('change', (next: AppStateStatus) => {
     if (next === 'background') {
-      disposeAllBackgroundConversationWs();
+      if (slot) {
+        scheduleBackgroundDisconnect();
+      }
+    } else if (next === 'active') {
+      cancelBackgroundDisconnectTimer();
     }
   });
-  backgroundUnsubscribe = () => sub.remove();
+  backgroundUnsubscribe = () => {
+    cancelBackgroundDisconnectTimer();
+    sub.remove();
+  };
 }
 
 function disposeSlot(): void {
   if (!slot) return;
   slot.session.dispose();
   slot = null;
+  for (const cb of slotDisposedListeners) {
+    try {
+      cb();
+    } catch {
+      /* listener 自行兜底 */
+    }
+  }
 }
 
 const offScreenUi = {
@@ -54,12 +100,14 @@ export function releaseConversationWsUi(
 /** 删除会话等场景：关闭对应长连 */
 export function disposeBackgroundConversationWs(conversationId: string): void {
   if (slot?.conversationId === conversationId) {
+    cancelBackgroundDisconnectTimer();
     disposeSlot();
   }
 }
 
 /** 登出 / 清账号：关闭池中连接 */
 export function disposeAllBackgroundConversationWs(): void {
+  cancelBackgroundDisconnectTimer();
   disposeSlot();
 }
 

app-expo/src/features/conversation/hooks.ts

@@ -1,7 +1,11 @@
 import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
 import { File, Paths } from 'expo-file-system';
 import { useCallback, useEffect, useRef, useState } from 'react';
-import { AppState, type AppStateStatus } from 'react-native';
+import {
+  AppState,
+  InteractionManager,
+  type AppStateStatus,
+} from 'react-native';
 
 import i18n from '@/i18n';
 import type { TopicSuggestion, WsConnectionState } from '@/core/ws/types';
@@ -9,9 +13,9 @@ import type { TopicSuggestion, WsConnectionState } from '@/core/ws/types';
 import { conversationApi } from './api';
 import {
   acquireBackgroundConversationWs,
-  disposeAllBackgroundConversationWs,
   disposeBackgroundConversationWs,
   releaseConversationWsUi,
+  subscribeConversationPoolSlotDisposed,
 } from './conversation-ws-background-pool';
 import { conversationMessagesRepository } from './conversation-messages-repository';
 import { conversationKeys } from './query-keys';
@@ -246,7 +250,10 @@ export function useRealtimeSession({
 
   const [foregroundResumeGeneration, setForegroundResumeGeneration] =
     useState(0);
-  const needsResumeAfterBackgroundRef = useRef(false);
+  const enabledRef = useRef(enabled);
+  const conversationIdRef = useRef(conversationId);
+  enabledRef.current = enabled;
+  conversationIdRef.current = conversationId;
 
   const handleStreamingText: StreamingTextCallback = useCallback(
     (text, isComplete) => {
@@ -295,21 +302,38 @@ export function useRealtimeSession({
   useEffect(() => {
     if (!enabled || !conversationId) return;
 
-    const sub = AppState.addEventListener('change', (next: AppStateStatus) => {
-      if (next === 'background') {
-        needsResumeAfterBackgroundRef.current = true;
-        disposeAllBackgroundConversationWs();
-        sessionRef.current = null;
-        setConnectionState('disconnected');
-        setStreamingMessage(null);
-        setAwaitingAssistantReply(false);
-      } else if (next === 'active' && needsResumeAfterBackgroundRef.current) {
-        needsResumeAfterBackgroundRef.current = false;
-        setForegroundResumeGeneration((g) => g + 1);
-      }
+    const unsubSlotDisposed = subscribeConversationPoolSlotDisposed(() => {
+      sessionRef.current = null;
+      setConnectionState('disconnected');
+      setStreamingMessage(null);
+      setAwaitingAssistantReply(false);
     });
 
-    return () => sub.remove();
+    const sub = AppState.addEventListener('change', (next: AppStateStatus) => {
+      if (next !== 'active') return;
+      /**
+       * 短切后台不断开时：若 TCP 已断则 connect()。
+       * 长后台已由池超时 dispose：此处 sessionRef 为空则重绑整段会话。
+       */
+      void InteractionManager.runAfterInteractions(() => {
+        if (!enabledRef.current || !conversationIdRef.current) {
+          return;
+        }
+        const s = sessionRef.current;
+        if (!s) {
+          setForegroundResumeGeneration((g) => g + 1);
+          return;
+        }
+        if (s.getConnectionState() === 'disconnected') {
+          void s.connect();
+        }
+      });
+    });
+
+    return () => {
+      unsubSlotDisposed();
+      sub.remove();
+    };
   }, [enabled, conversationId]);
 
   /**