callkit

CallKit

Build VoIP calling features that integrate with the native iOS call UI using CallKit and PushKit. Covers incoming/outgoing call flows, VoIP push registration, audio session coordination, and call directory extensions. Targets Swift 6.3 / iOS 26+.

Contents

• Setup
• Provider Configuration
• Incoming Call Flow
• Outgoing Call Flow
• PushKit VoIP Registration
• Audio Session Coordination
• Call Directory Extension and Manager
• Common Mistakes
• Review Checklist
• References

Setup

Project Configuration

1. Enable the Voice over IP background mode in Signing & Capabilities
2. Add the Push Notifications capability
3. For call directory extensions, add a Call Directory Extension target

Key Types

Provider Configuration

Create a single CXProvider at app launch and keep it alive for the app lifetime. Configure it with a CXProviderConfiguration that describes your calling capabilities.

import CallKit

/// CXProvider dispatches all delegate calls to the queue passed to `setDelegate(_:queue:)`.
/// The `let` properties are initialized once and never mutated, making this type
/// safe to share across concurrency domains despite @unchecked Sendable.
final class CallManager: NSObject, @unchecked Sendable {
    static let shared = CallManager()

    let provider: CXProvider
    let callController = CXCallController()

    private override init() {
        let config = CXProviderConfiguration()
        config.localizedName = "My VoIP App"
        config.supportsVideo = true
        config.maximumCallsPerCallGroup = 1
        config.maximumCallGroups = 2
        config.supportedHandleTypes = [.phoneNumber, .emailAddress]
        config.includesCallsInRecents = true

        provider = CXProvider(configuration: config)
        super.init()
        provider.setDelegate(self, queue: nil)
    }
}

Incoming Call Flow

When a required VoIP call push arrives, report the incoming call to CallKit immediately. The system displays the native call UI. You must report required calls before the PushKit completion handler returns -- failure to do so causes the system to terminate your app.

func reportIncomingCall(
    uuid: UUID,
    handle: String,
    hasVideo: Bool
) async throws {
    let update = CXCallUpdate()
    update.remoteHandle = CXHandle(type: .phoneNumber, value: handle)
    update.hasVideo = hasVideo
    update.localizedCallerName = "Jane Doe"

    try await withCheckedThrowingContinuation {
        (continuation: CheckedContinuation<Void, Error>) in
        provider.reportNewIncomingCall(
            with: uuid,
            update: update
        ) { error in
            if let error {
                continuation.resume(throwing: error)
            } else {
                continuation.resume()
            }
        }
    }
}

Handling the Answer Action

Implement CXProviderDelegate to respond when the user answers:

extension CallManager: CXProviderDelegate {
    func providerDidReset(_ provider: CXProvider) {
        // End all calls, reset audio
    }

    func provider(_ provider: CXProvider, perform action: CXAnswerCallAction) {
        // Prepare audio, then fulfill only after the call is actually ready
        configureAudioSession()
        connectToCallServer(callUUID: action.callUUID) { success in
            if success {
                action.fulfill()
            } else {
                provider.reportCall(
                    with: action.callUUID,
                    endedAt: Date(),
                    reason: .failed
                )
                action.fail()
            }
        }
    }

    func provider(_ provider: CXProvider, perform action: CXEndCallAction) {
        disconnectFromCallServer(callUUID: action.callUUID)
        action.fulfill()
    }
}

Outgoing Call Flow

Use CXCallController to request an outgoing call. The system routes the request through your CXProviderDelegate.

func startOutgoingCall(handle: String, hasVideo: Bool) {
    let uuid = UUID()
    let handle = CXHandle(type: .phoneNumber, value: handle)
    let startAction = CXStartCallAction(call: uuid, handle: handle)
    startAction.isVideo = hasVideo

    let transaction = CXTransaction(action: startAction)
    callController.request(transaction) { error in
        if let error {
            print("Failed to start call: \(error)")
        }
    }
}

Delegate Methods for Outgoing Calls

extension CallManager {
    func provider(_ provider: CXProvider, perform action: CXStartCallAction) {
        configureAudioSession()
        // Begin connecting to server
        provider.reportOutgoingCall(
            with: action.callUUID,
            startedConnectingAt: Date()
        )

        connectToServer(callUUID: action.callUUID) {
            provider.reportOutgoingCall(
                with: action.callUUID,
                connectedAt: Date()
            )
        }
        action.fulfill()
    }
}

PushKit VoIP Registration

Register for VoIP pushes at every app launch and send token changes to your server. For iOS 13 SDK+ apps, every report-required VoIP call push must be reported before PushKit completion using CallKit, or LiveCommunicationKit for apps built on that framework. On iOS 26.4+, PKVoIPPushMetadata.mustReport is the gate: true means report before completion; false means no CallKit or LiveCommunicationKit report is required. Missing a required report before completion can terminate the app, and repeated failures may stop VoIP delivery.

import PushKit

final class PushManager: NSObject, PKPushRegistryDelegate {
    let registry: PKPushRegistry

    override init() {
        registry = PKPushRegistry(queue: .main)
        super.init()
        registry.delegate = self
        registry.desiredPushTypes = [.voIP]
    }

    func pushRegistry(
        _ registry: PKPushRegistry,
        didUpdate pushCredentials: PKPushCredentials,
        for type: PKPushType
    ) {
        let token = pushCredentials.token
            .map { String(format: "%02x", $0) }
            .joined()
        // Send token to your server
        sendTokenToServer(token)
    }

    @available(iOS 26.4, *)
    func pushRegistry(
        _ registry: PKPushRegistry,
        didReceiveIncomingVoIPPushWith payload: PKPushPayload,
        metadata: PKVoIPPushMetadata,
        withCompletionHandler completion: @escaping @Sendable () -> Void
    ) {
        guard metadata.mustReport else {
            completion()
            return
        }
        handleIncomingVoIPPush(payload, completion: completion)
    }

    // Keep the older callback for iOS 26.0-26.3 and older deployment targets.
    func pushRegistry(
        _ registry: PKPushRegistry,
        didReceiveIncomingPushWith payload: PKPushPayload,
        for type: PKPushType,
        completion: @escaping () -> Void
    ) {
        guard type == .voIP else {
            completion()
            return
        }

        handleIncomingVoIPPush(payload, completion: completion)
    }

    private func handleIncomingVoIPPush(
        _ payload: PKPushPayload,
        completion: @escaping () -> Void
    ) {
        let callUUID = UUID()
        let handle = payload.dictionaryPayload["handle"] as? String ?? "Unknown"

        Task {
            do {
                try await CallManager.shared.reportIncomingCall(
                    uuid: callUUID,
                    handle: handle,
                    hasVideo: false
                )
            } catch {
                // Call was filtered by DND or block list
            }
            completion()
        }
    }
}

Server-side VoIP pushes should use a short lifetime: set apns-expiration to 0 or only a few seconds. After the initial push wakes the app, send hangups and call-detail changes over the app-server connection instead of sending more VoIP pushes.

Audio Session Coordination

CallKit manages audio session activation/deactivation. Configure your audio session when CallKit tells you to, not before. Review answers should name both sides: start media only in provider(_:didActivate:), and stop/tear down media in provider(_:didDeactivate:) or reset paths.

extension CallManager {
    func provider(_ provider: CXProvider, didActivate audioSession: AVAudioSession) {
        // Audio session is now active -- start audio engine / WebRTC
        startAudioEngine()
    }

    func provider(_ provider: CXProvider, didDeactivate audioSession: AVAudioSession) {
        // Audio session deactivated -- stop audio engine
        stopAudioEngine()
    }

    func configureAudioSession() {
        let session = AVAudioSession.sharedInstance()
        do {
            try session.setCategory(
                .playAndRecord,
                mode: .voiceChat,
                options: [.allowBluetooth, .allowBluetoothA2DP]
            )
        } catch {
            print("Audio session configuration failed: \(error)")
        }
    }
}

Call Directory Extension and Manager

Use Call Directory for preloaded caller ID/blocking, not per-call API lookup. The extension loads sorted bulk data in beginRequest(with:); the main app uses CXCallDirectoryManager to check enabled status, open Call Blocking & Identification settings when disabled, and reload after data changes. Store CXCallDirectoryPhoneNumber as country code plus digits in ascending order (for example 18005551234), not a formatted string.

import CallKit

final class CallDirectoryHandler: CXCallDirectoryProvider {
    override func beginRequest(
        with context: CXCallDirectoryExtensionContext
    ) {
        if context.isIncremental {
            addOrRemoveIncrementalEntries(to: context)
        } else {
            addAllEntries(to: context)
        }
        context.completeRequest()
    }

    private func addAllEntries(
        to context: CXCallDirectoryExtensionContext
    ) {
        // Country code + digits, sorted in ascending order
        let blockedNumbers: [CXCallDirectoryPhoneNumber] = [
            18005551234, 18005555678
        ]
        for number in blockedNumbers {
            context.addBlockingEntry(
                withNextSequentialPhoneNumber: number
            )
        }

        let identifiedNumbers: [(CXCallDirectoryPhoneNumber, String)] = [
            (18005551111, "Local Pizza"),
            (18005552222, "Dentist Office")
        ]
        for (number, label) in identifiedNumbers {
            context.addIdentificationEntry(
                withNextSequentialPhoneNumber: number,
                label: label
            )
        }
    }
}

Main-App Manager: Status, Settings, Reload

let manager = CXCallDirectoryManager.sharedInstance
manager.getEnabledStatusForExtension(withIdentifier: extensionID) { status, _ in
    guard status == .enabled else {
        manager.openSettings { _ in } // Call Blocking & Identification
        return
    }
    manager.reloadExtension(withIdentifier: extensionID) { _ in }
}

Check getEnabledStatusForExtension(...) before assuming the extension is active, use openSettings(...) for Call Blocking & Identification when disabled, and call reloadExtension(...) after data changes. Route APNs auth-key rotation and normal remote-notification setup to push-notifications.

Common Mistakes

DON'T: Fail to report a required call on VoIP push receipt

Follow the PushKit report rules above: iOS 13 SDK+ apps must report report-required VoIP call pushes before completion, and on iOS 26.4+ PKVoIPPushMetadata.mustReport identifies which pushes are required. Missing a required report can terminate the app; repeated failures may stop VoIP delivery.

Do not treat a required VoIP push as a data-only notification. Report the call to CallKit and call the PushKit completion handler from the report completion.

DON'T: Fulfill answer before the call is connected

When the user answers before your app has established the server/media connection, leave the CXAnswerCallAction pending while connecting. Fulfill it after the call is ready; if connection fails, fail the action and report the call ended with .failed.

DON'T: Start audio before CallKit activates the session

Starting your audio engine before provider(_:didActivate:) causes silence or immediate deactivation. CallKit manages session priority with the system.

Prepare audio in the answer/start action if needed, then start media only from provider(_:didActivate:).

For iOS 26 call translation, set CXProviderConfiguration.supportsAudioTranslation when your service supports it and handle CXSetTranslatingCallAction. If a person mutes during a translated call, mute app input with CXSetMutedCallAction; do not deactivate upstream audio that translated audio depends on.

For encrypted VoIP metadata, use CXProvider.reportNewIncomingVoIPPushPayload only from a notification service extension when the server cannot determine whether encrypted content is a VoIP call or other data. That path requires the com.apple.developer.usernotifications.filtering entitlement; otherwise send a normal PushKit VoIP push.

DON'T: Forget to call action.fulfill() or action.fail()

Failing to fulfill or fail an action leaves the call in a limbo state and triggers the timeout handler.

Every provider action path must eventually call fulfill() or fail(), including network-error and cancellation paths.

DON'T: Ignore push token refresh

The VoIP push token can change at any time. If your server has a stale token, pushes silently fail and incoming calls never arrive.

Send the token to your server every time didUpdate pushCredentials fires, not just during first-run onboarding.

DON'T: Use Call Directory for per-call lookup

Call Directory extensions provide preloaded caller ID and blocking data. They cannot ask a web service for the incoming caller during call presentation. Fetch or generate the dataset ahead of time, reload the extension, and add entries in sorted sequential order.

Review Checklist

• [ ] VoIP background mode enabled in capabilities
• [ ] Single CXProvider instance created at app launch and retained
• [ ] CXProviderDelegate set before reporting any calls
• [ ] iOS 26.4+ PushKit path reports when mustReport is true and may skip when false
• [ ] iOS 13 SDK+ PushKit VoIP call pushes report to CallKit before completion
• [ ] VoIP APNs requests use apns-expiration of 0 or only a few seconds
• [ ] Hangups and detail updates use the app-server connection after the initial push
• [ ] action.fulfill() or action.fail() called for every provider delegate action
• [ ] CXAnswerCallAction fulfilled only after the call server/media connection is ready
• [ ] Audio engine started only after provider(_:didActivate:) callback
• [ ] Audio engine stopped in provider(_:didDeactivate:) callback
• [ ] Audio session category set to .playAndRecord with .voiceChat mode
• [ ] VoIP push token sent to server on every didUpdate pushCredentials callback
• [ ] PKPushRegistry created at every app launch (not lazily)
• [ ] Call Directory data is preloaded, not fetched per incoming call
• [ ] CXCallDirectoryPhoneNumber documented as country calling code + digits
• [ ] CXCallDirectoryManager names status check, reload, and settings-opening APIs
• [ ] CXCallUpdate populated with localizedCallerName and remoteHandle
• [ ] Outgoing calls report startedConnectingAt and connectedAt timestamps
• [ ] iOS 26 call translation keeps upstream audio active during mute
• [ ] Encrypted metadata filtering mentions the notification service extension entitlement

References

• Extended patterns (hold, mute, group calls, delegate lifecycle): references/callkit-patterns.md
• CallKit framework
• CXProvider
• CXCallController
• CXCallAction
• CXCallUpdate
• CXProviderConfiguration
• CXProviderDelegate
• PKPushRegistry
• PKPushRegistryDelegate
• PKVoIPPushMetadata
• CXCallDirectoryProvider
• CXCallDirectoryPhoneNumber
• CXCallDirectoryManager
• CXSetTranslatingCallAction
• reportNewIncomingVoIPPushPayload(_:completion:))
• Making and receiving VoIP calls
• Responding to VoIP Notifications from PushKit