Core Bluetooth

Bluetooth Low Energy on Apple platforms: discovering and talking to BLE peripherals (central role) and advertising your own services (peripheral role). The deep API reference — full central/peripheral managers, GATT, async/await wrappers, notifications via AsyncStream, SwiftUI patterns, background/state-restoration, and battery/security practices — lives in references/guide.md. This file is the decision and discipline layer: read it first, open the guide for specifics.

Dials

Set these explicitly at the start; they change what "correct" means.

1. ROLE — central (default; you scan for and drive remote peripherals) · peripheral (CBPeripheralManager; your device advertises services and answers reads/writes) · both (device-to-device).
2. LIFECYCLE — foreground (default; scan/connect only while the app is active) · background (UIBackgroundModes = bluetooth-central/bluetooth-peripheral + state preservation/restoration with a restore identifier).
3. PAIRING_UX — manual (your own scan list + connect flow, full control) · accessorysetupkit (iOS 18+ system discovery sheet for a known accessory — better UX, scoped permission).

When to use

Building or reviewing any BLE code that talks to Core Bluetooth directly: scanning, connecting, discovering services/characteristics, reading/writing/notifying, or advertising as a peripheral. If the task is purely the onboarding/pairing UX for a specific accessory, prefer AccessorySetupKit and only drop to raw Core Bluetooth for the data plane.

Core rules