Port to Swift 6

OptableSDK.podspec

@@ -15,7 +15,7 @@ Pod::Spec.new do |spec|
 
   spec.platform              = :ios
   spec.ios.deployment_target = "15.0"
-  spec.swift_version         = "5.0"
+  spec.swift_version         = "6.0"
 
   spec.source        = { :git => "https://github.com/Optable/optable-ios-sdk.git", :tag => "#{spec.version}" }
   spec.source_files  = "Source/**/*.{h,m,swift}"

OptableSDK.xcodeproj/project.pbxproj

@@ -388,7 +388,7 @@
 				SUPPORTS_MACCATALYST = NO;
 				SWIFT_ACTIVE_COMPILATION_CONDITIONS = DEBUG;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 				TARGETED_DEVICE_FAMILY = "1,2";
 			};
 			name = Debug;
@@ -419,7 +419,7 @@
 				PRODUCT_NAME = "$(TARGET_NAME:c99extidentifier)";
 				SKIP_INSTALL = YES;
 				SUPPORTS_MACCATALYST = NO;
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 				TARGETED_DEVICE_FAMILY = "1,2";
 			};
 			name = Release;
@@ -431,7 +431,7 @@
 				CODE_SIGN_STYLE = Automatic;
 				DEVELOPMENT_TEAM = "";
 				INFOPLIST_FILE = Tests/Info.plist;
-				IPHONEOS_DEPLOYMENT_TARGET = 15.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 17.0;
 				LD_RUNPATH_SEARCH_PATHS = (
 					"$(inherited)",
 					"@executable_path/Frameworks",
@@ -440,7 +440,7 @@
 				PRODUCT_BUNDLE_IDENTIFIER = co.optable.OptableSDKTests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				PROVISIONING_PROFILE_SPECIFIER = "";
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 				TARGETED_DEVICE_FAMILY = "1,2";
 			};
 			name = Debug;
@@ -452,7 +452,7 @@
 				CODE_SIGN_STYLE = Automatic;
 				DEVELOPMENT_TEAM = "";
 				INFOPLIST_FILE = Tests/Info.plist;
-				IPHONEOS_DEPLOYMENT_TARGET = 15.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 17.0;
 				LD_RUNPATH_SEARCH_PATHS = (
 					"$(inherited)",
 					"@executable_path/Frameworks",
@@ -461,7 +461,7 @@
 				PRODUCT_BUNDLE_IDENTIFIER = co.optable.OptableSDKTests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				PROVISIONING_PROFILE_SPECIFIER = "";
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 				TARGETED_DEVICE_FAMILY = "1,2";
 			};
 			name = Release;

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.5
+// swift-tools-version:6.0
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription
@@ -29,5 +29,6 @@ let package = Package(
             name: "OptableSDKTests",
             dependencies: ["OptableSDK"],
             path: "Tests"),
-    ]
+    ],
+    swiftLanguageModes: [.v6]
 )

Source/Core/EdgeAPI.swift

@@ -16,25 +16,34 @@ import WebKit
  [](https://docs.optable.co/optable-documentation/guides/real-time-api-integrations-guide)
 
  */
-final class EdgeAPI {
-    private let kPassportHeader: String = "X-Optable-Visitor"
+final class EdgeAPI: Sendable {
+    private static let kPassportHeader: String = "X-Optable-Visitor"
 
-    var storage: LocalStorage
-    var config: OptableConfig
+    let storage: LocalStorage
+    let config: OptableConfig
 
-    var userAgent: String?
+    /// The `User-Agent` sent with every request: `config.customUserAgent` when set, otherwise the WebView's
+    /// user agent, resolved asynchronously on the main actor at init (nil until it arrives).
+    var userAgent: String? {
+        get { userAgentStore.withLock { $0 } }
+        set { userAgentStore.withLock { $0 = newValue } }
+    }
+
+    private let userAgentStore: Locked<String?>
 
-    private lazy var jsonEncoder = JSONEncoder()
+    private let jsonEncoder = JSONEncoder()
 
     init(_ config: OptableConfig) {
         self.config = config
         self.storage = LocalStorage(config)
+        self.userAgentStore = Locked(config.customUserAgent)
+
         if config.customUserAgent == nil {
-            self.resolveUserAgent { realUserAgent in
-                self.userAgent = realUserAgent
+            let userAgentStore = self.userAgentStore
+            Task { @MainActor in
+                let realUserAgent = await EdgeAPI.resolveWebViewUserAgent()
+                userAgentStore.withLock { $0 = realUserAgent }
             }
-        } else {
-            self.userAgent = config.customUserAgent
         }
     }
 
@@ -108,8 +117,8 @@ final class EdgeAPI {
 
 // MARK: - Dispatch
 extension EdgeAPI {
-    func dispatch(request: URLRequest, completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void) -> URLSessionDataTask {
-        return URLSession.shared.dataTask(with: request) { data, response, error in
+    func dispatch(request: URLRequest, completionHandler: @escaping @Sendable (Data?, URLResponse?, Error?) -> Void) -> URLSessionDataTask {
+        return URLSession.shared.dataTask(with: request) { [storage] data, response, error in
             guard let res = response as? HTTPURLResponse, error == nil else {
                 completionHandler(data, response, error)
                 return
@@ -118,8 +127,8 @@ extension EdgeAPI {
                 completionHandler(data, response, error)
                 return
             }
-            if let passport = res.value(forHTTPHeaderField: self.kPassportHeader) {
-                self.storage.setPassport(passport)
+            if let passport = res.value(forHTTPHeaderField: Self.kPassportHeader) {
+                storage.setPassport(passport)
             }
             completionHandler(data, response, error)
         }
@@ -128,30 +137,26 @@ extension EdgeAPI {
 
 // MARK: - Private
 extension EdgeAPI {
-    private func resolveUserAgent(callback: @escaping (_ useragent: String) -> Void) {
-        var wkUserAgent = ""
-        let myGroup = DispatchGroup()
+    /// Reads `navigator.userAgent` from a hidden, throwaway WKWebView attached to the key window.
+    /// Returns an empty string when the WebView cannot provide one.
+    @MainActor
+    private static func resolveWebViewUserAgent() async -> String {
         let window = UIApplication.shared.connectedScenes
             .compactMap { ($0 as? UIWindowScene)?.keyWindow }
             .first
         let webView = WKWebView(frame: UIScreen.main.bounds)
 
         webView.isHidden = true
         window?.addSubview(webView)
-        myGroup.enter()
-
-        webView.loadHTMLString("<html></html>", baseURL: nil)
-        webView.evaluateJavaScript("navigator.userAgent", completionHandler: { (userAgent: Any?, error: Error?) in
-            if let userAgent = userAgent as? String {
-                wkUserAgent = userAgent
-            }
+        defer {
             webView.stopLoading()
             webView.removeFromSuperview()
-            myGroup.leave()
-        })
-        myGroup.notify(queue: .main) {
-            callback(wkUserAgent)
         }
+
+        webView.loadHTMLString("<html></html>", baseURL: nil)
+
+        let userAgent = try? await webView.evaluateJavaScript("navigator.userAgent")
+        return (userAgent as? String) ?? ""
     }
 
     func resolveHeaders() -> HTTPHeaders {
@@ -172,7 +177,7 @@ extension EdgeAPI {
         }
 
         if let passport: String = storage.getPassport() {
-            headers[kPassportHeader] = passport
+            headers[Self.kPassportHeader] = passport
         }
 
         return headers

Source/Core/LocalStorage.swift

@@ -10,20 +10,21 @@ import Foundation
 
 /**
  The OptableSDK keeps some state in UserDefaults (https://developer.apple.com/documentation/foundation/userdefaults), a key/value store persisted across launches of the app. The state is therefore unique to the app+device, and not globally unique to the app across devices.
+
+ `Sendable`: every stored property is immutable, `UserDefaults` is thread-safe, and targeting reads and writes
+ are serialized by `lock`.
  */
-final class LocalStorage: NSObject {
+final class LocalStorage: NSObject, Sendable {
     private let targetingDataKey: String
     private let gamTargetingKeywordsKey: String
     private let ortb2Key: String
     private let id5SignatureKey: String
 
     let keyPfx: String = "OPTABLE"
-    var passportKey: String
-    var targetingKey: String
-    var targetingStoredAtKey: String
-
-    private let config: OptableConfig
-
+    let passportKey: String
+    let targetingKey: String
+    let targetingStoredAtKey: String
+
     private let lock = NSLock()
 
     init(_ config: OptableConfig) {
@@ -33,8 +34,6 @@ final class LocalStorage: NSObject {
             .data(using: .utf8)?
             .base64EncodedString()
 
-        self.config = config
-
         self.passportKey = self.keyPfx + "_PASS_" + (base64Key ?? "UNKNOWN")
         self.targetingKey = self.keyPfx + "_TGT_" + (base64Key ?? "UNKNOWN")
 
@@ -53,13 +52,15 @@ final class LocalStorage: NSObject {
         UserDefaults.standard.set(passport, forKey: passportKey)
     }
 
-    func getTargeting() -> OptableTargeting? {
+    /// Returns the stored targeting entry while it is younger than `cacheTTL`. An expired entry is removed
+    /// from storage and reported as absent.
+    func getTargeting(cacheTTL: TimeInterval) -> OptableTargeting? {
         lock.synchronized {
             guard let targetingData = UserDefaults.standard.object(forKey: targetingDataKey) as? [String: Any] else {
                 return nil
             }
 
-            guard isTargetingFresh() else {
+            guard isTargetingFresh(cacheTTL: cacheTTL) else {
                 removeTargetingEntry()
                 return nil
             }
@@ -105,15 +106,15 @@ final class LocalStorage: NSObject {
         UserDefaults.standard.removeObject(forKey: targetingStoredAtKey)
     }
 
-    /// Whether the stored targeting entry was fetched recently enough to still be served, per `config.cacheTTL`. The caller must hold `lock`.
-    private func isTargetingFresh() -> Bool {
+    /// Whether the stored targeting entry was fetched recently enough to still be served, per `cacheTTL`. The caller must hold `lock`.
+    private func isTargetingFresh(cacheTTL: TimeInterval) -> Bool {
         // NOTE: A missing timestamp means the entry predates cache expiry support, so its age is unknowable - treat it as expired.
         guard let storedAt = UserDefaults.standard.object(forKey: targetingStoredAtKey) as? TimeInterval else {
             return false
         }
 
         let age = Date().timeIntervalSince1970 - storedAt
 
-        return age >= 0 && age < config.cacheTTL
+        return age >= 0 && age < cacheTTL
     }
 }

Source/Misc/AppTrackingTransparency.swift

@@ -11,11 +11,18 @@
     import AppTrackingTransparency
     import Foundation
 
+    /// The `*_DebugOverride` knobs are test-only hooks. Each one is backed by a `Locked` box, which keeps
+    /// the static accessors concurrency-safe under Swift 6 (plain `static var`s are rejected there).
     enum ATT {
         // MARK: advertisingIdentifier
 
         #if DEBUG
-            static var advertisingIdentifier_DebugOverride: UUID?
+            private static let _advertisingIdentifier_DebugOverride = Locked<UUID?>(nil)
+            static var advertisingIdentifier_DebugOverride: UUID? {
+                get { _advertisingIdentifier_DebugOverride.withLock { $0 } }
+                set { _advertisingIdentifier_DebugOverride.withLock { $0 = newValue } }
+            }
+
             static var advertisingIdentifier: UUID {
                 advertisingIdentifier_DebugOverride ?? ASIdentifierManager.shared().advertisingIdentifier
             }
@@ -28,7 +35,11 @@
         // MARK: advertisingIdentifierAvailable
 
         #if DEBUG
-            static var advertisingIdentifierAvailable_DebugOverride: Bool?
+            private static let _advertisingIdentifierAvailable_DebugOverride = Locked<Bool?>(nil)
+            static var advertisingIdentifierAvailable_DebugOverride: Bool? {
+                get { _advertisingIdentifierAvailable_DebugOverride.withLock { $0 } }
+                set { _advertisingIdentifierAvailable_DebugOverride.withLock { $0 = newValue } }
+            }
         #endif
 
         static var advertisingIdentifierAvailable: Bool {
@@ -44,7 +55,11 @@
         // MARK: trackingStatus
 
         #if DEBUG
-            static var trackingStatus_DebugOverride: ATTrackingManager.AuthorizationStatus?
+            private static let _trackingStatus_DebugOverride = Locked<ATTrackingManager.AuthorizationStatus?>(nil)
+            static var trackingStatus_DebugOverride: ATTrackingManager.AuthorizationStatus? {
+                get { _trackingStatus_DebugOverride.withLock { $0 } }
+                set { _trackingStatus_DebugOverride.withLock { $0 = newValue } }
+            }
         #endif
 
         static var trackingStatus: ATTrackingManager.AuthorizationStatus {

Source/Misc/Locked.swift

@@ -0,0 +1,28 @@
+//
+//  Locked.swift
+//  OptableSDK
+//
+//  Copyright © 2026 Optable Technologies, Inc. All rights reserved.
+//
+
+import Foundation
+
+/// A value guarded by a lock, so it can be shared across threads under Swift 6 strict concurrency.
+/// Stands in for `Synchronization.Mutex` (iOS 18) and `OSAllocatedUnfairLock` (iOS 16).
+final class Locked<Value> {
+    private let lock = NSLock()
+    private var value: Value
+
+    init(_ value: Value) {
+        self.value = value
+    }
+
+    /// Runs `body` with exclusive access to the wrapped value and returns its result.
+    func withLock<T>(_ body: (inout Value) throws -> T) rethrows -> T {
+        lock.lock()
+        defer { lock.unlock() }
+        return try body(&value)
+    }
+}
+
+extension Locked: @unchecked Sendable where Value: Sendable {}