LiveCommunicationKit: In‑call banner missing in foreground, only appears after app goes background (iPhone14 Pro)

Environment:

• Device: iPhone 14 Pro
• iOS version: 26
• SDK: LiveCommunicationKit
• App status: Foreground / Active state
• Problem reproduction: Intermittent, happens on some devices, not 100% reproducible on all test devices.

Expected behavior: Incoming call banner should present when app is active (foreground).

Actual behavior: No system incoming‑call banner while app is foreground. Banner appears only after pressing home‑button / switching app to background.

Additional notes: Our app uses LiveCommunicationKit because VoIP PushKit is not permitted for China mainland App Store distribution. Call reporting completes without error; no error returned from LiveCommunicationKit API.

    private func _lckReportIncomingCall(call: Call?, uuid: UUID, handle: String, hasVideo: Bool, displayName: String) {
        guard let manager = conversationManager else {
            Log.error("[ProviderDelegate-LCK] ConversationManager is nil, falling back")
            _fallbackReportIncomingCall(call: call, uuid: uuid, handle: handle, hasVideo: hasVideo, displayName: displayName)
            return
        }
        
        let callInfo = callInfos[uuid]
        let callId = callInfo?.callId ?? ""
        
        let remoteHandle = Handle(type: .generic, value: handle, displayName: displayName)
        let update = Conversation.Update(localMember: nil, members: [remoteHandle], activeRemoteMembers: [remoteHandle])
        
        // 冷启动时 iOS PKPushRegistry 要求在 2 秒内上报来电，否则杀进程。
        // Task { @MainActor } 是异步的，调试时主线程 RunLoop 来不及调度就超时了。
        // 这里用 DispatchSemaphore 在后台线程同步等待 LCK 上报完成。
        let semaphore = DispatchSemaphore(value: 0)
        var lckError: Error?
        
        DispatchQueue.main.async {
            Task { @MainActor in
                do {
                    try await manager.reportNewIncomingConversation(uuid: uuid, update: update)
                    Log.info("[ProviderDelegate-LCK] Reported incoming conversation: callId=\(callId), uuid=\(uuid)")
                    
                    if TelecomManager.shared.endCallkit {
                        CoreContext.shared.doOnCoreQueue(synchronous: true) { core in
                            let linphoneCall = core.getCallByCallid(callId: callId)
                            if linphoneCall?.state == .PushIncomingReceived {
                                try? linphoneCall?.terminate()
                            }
                        }
                    }
                } catch {
                    Log.error("[ProviderDelegate-LCK] Failed to report incoming conversation: \(error)")
                    lckError = error
                }
                semaphore.signal()
            }
        }
        
        let waitResult = semaphore.wait(timeout: .now() + 5)
        if waitResult == .timedOut {
            Log.error("[ProviderDelegate-LCK] Timed out waiting for LCK report, falling back")
            _fallbackReportIncomingCall(call: call, uuid: uuid, handle: handle, hasVideo: hasVideo, displayName: displayName)
        } else if let error = lckError {
            Log.error("[ProviderDelegate-LCK] LCK report failed: \(error), declining SIP call")
            // 来电被拒（勿扰/黑名单等），decline 掉 SIP 侧
            CoreContext.shared.doOnCoreQueue(synchronous: true) { _ in
                try? call?.decline(reason: .Busy)
            }
        }
    }