# AccessoryGPUWorker.FeatureSession.Handler A handler type for the session’s transport extension. ``` typealias Handler = AccessoryFeatureRuntimeSessionHandler ``` ## Discussion Create a handler type that conforms to this type alias to receive events from an [`AccessoryGPUWorker.FeatureSession`](/documentation/AccessoryTransportExtension/AccessoryGPUWorker/FeatureSession). Because each feature declares its own `Handler` type alias, your transport extension needs a distinct handler type for each feature it supports: the compiler rejects a handler written for [`AccessoryWorker.FeatureSession`](/documentation/AccessoryTransportExtension/AccessoryWorker/FeatureSession) if you pass it to the feature’s session, or any other feature’s session. Return an instance of your handler from the factory closure that you pass to [`makeFeatureSession(_:)`](/documentation/AccessoryTransportExtension/AccessoryTransportSession/makeFeatureSession(_:)). --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)