AudioAccessoryKit

Participate in Apple's seamless audio ecosystem, automatic audio routing, and head/ear placement detection for third-party audio accessories. Targets Swift 6.3 / iOS 26+.

Prerequisite: Audio accessories must be paired and authorized via AccessorySetupKit before configuring with AudioAccessoryKit.

Contents

• Core Concepts & Prerequisites
• Registering Accessory Control Devices
• Device Capabilities & Configuration
• Monitoring Placement State
• Audio Routing Coordination
• Common Mistakes
• Review Checklist
• References

Core Concepts & Prerequisites

AudioAccessoryKit bridges authorized Bluetooth accessories into iOS system audio management:

1. Discover and pair the hardware using AccessorySetupKit.
2. Wrap the authorized peripheral in an AccessoryControlDevice.
3. Register device capabilities (ANC, spatial audio, ear detection).
4. Update live placement state (in-ear, in-case, on-head) so iOS can dynamically switch audio routes.

Registering Accessory Control Devices

Register an AccessoryControlDevice for an authorized accessory:

import AudioAccessoryKit
import AccessorySetupKit

func configureAudioAccessory(accessory: ASAccessory) async throws {
    guard let btIdentifier = accessory.bluetoothIdentifier else { return }

    var config = AccessoryControlDevice.Configuration()
    config.capabilities = [.earDetection, .noiseControl, .spatialAudio]

    let device = try await AccessoryControlDevice.register(
        identifier: btIdentifier,
        configuration: config
    )
}

Device Capabilities & Configuration

Configure active hardware capabilities and audio listening modes:

var capabilities = AccessoryControlDevice.Capabilities()
capabilities.insert(.noiseControl)
capabilities.insert(.spatialAudio)

// Update listening mode
func setListeningMode(_ mode: AccessoryControlDevice.ListeningMode, on device: AccessoryControlDevice) async throws {
    try await device.updateListeningMode(mode)
}

Monitoring Placement State

Report hardware placement transitions (e.g. user inserts earbud) to trigger automatic audio switching:

func reportEarPlacement(inEar: Bool, device: AccessoryControlDevice) async throws {
    let placement: AccessoryControlDevice.Placement = inEar ? .inEar : .outOfEar
    try await device.updatePlacement(placement)
}

Audio Routing Coordination

When earbuds are placed in-ear, iOS automatically activates the audio route if automatic switching is enabled by the user in Settings.

Common Mistakes

• Calling AudioAccessoryKit before AccessorySetupKit authorization: An accessory must be paired through ASAccessorySession first.
• Reporting placement changes without hardware confirmation: Speculative placement updates disrupt active phone calls or media playback.
• Failing to register supported capabilities: Features like Spatial Audio or ANC fail to appear in Control Center if omitted from Configuration.capabilities.
• Assuming simulator execution: Audio accessory hardware integration requires physical testing on supported devices.

Review Checklist

• Hardware successfully paired via AccessorySetupKit before registration
• AccessoryControlDevice.Configuration accurately declares hardware capabilities
• Ear/head placement updates sent immediately upon hardware state change
• Audio route switching tested alongside active media playback

References

• Extended patterns (registration flow, placement monitoring, multi-device coordination): references/audioaccessorykit-patterns.md
• AudioAccessoryKit framework
• Supporting automatic audio switching
• AccessoryControlDevice
• AccessoryControlDevice registration
• AccessoryControlDevice lookup
• AccessoryControlDevice update
• AccessoryControlDevice.Configuration
• AccessoryControlDevice.Capabilities
• AccessoryControlDevice.Placement
• AccessorySetupKit framework (prerequisite for pairing)