feat: add config option to disable swizzling

CHANGELOG.md

@@ -1,8 +1,14 @@
 ## Next
 
+- feat: add config option to disable swizzling ([#388](https://github.com/PostHog/posthog-ios/pull/388))
+- feat: SDK instance now manages its own session ([#388](https://github.com/PostHog/posthog-ios/pull/388))
+> **Note**: A potentially breaking change for users with multiple SDK instances. Each SDK instance now manages its own `$session_id` instead of sharing a global session across all instances.
+> This aligns with PostHog JS SDK behavior and ensures proper session isolation when using multiple SDK instances.
+> For single-instance usage (the common case), this change has no impact.
+
 ## 3.33.0 - 2025-10-13
 
-- add evaluation tags to iOS SDK ([#387](https://github.com/PostHog/posthog-ios/pull/387))
+- feat: add evaluation tags to iOS SDK ([#387](https://github.com/PostHog/posthog-ios/pull/387))
 
 ## 3.32.0 - 2025-10-03
 

PostHog/App Life Cycle/PostHogAppLifeCycleIntegration.swift

@@ -17,6 +17,8 @@ import Foundation
  - captures an `App Backgrounded` event when the app moves to the background
  */
 final class PostHogAppLifeCycleIntegration: PostHogIntegration {
+    var requiresSwizzling: Bool { false }
+
     private static var integrationInstalledLock = NSLock()
     private static var integrationInstalled = false
     private static var didCaptureAppInstallOrUpdate = false

PostHog/Autocapture/PostHogAutocaptureIntegration.swift

@@ -11,6 +11,8 @@
     private let elementsChainDelimiter = ";"
 
     class PostHogAutocaptureIntegration: AutocaptureEventProcessing, PostHogIntegration {
+        var requiresSwizzling: Bool { true }
+
         private static var integrationInstalledLock = NSLock()
         private static var integrationInstalled = false
 

PostHog/DI.swift

@@ -10,8 +10,6 @@ enum DI {
     static var main = Container()
 
     final class Container {
-        // manages session rotation
-        lazy var sessionManager: PostHogSessionManager = .init()
         // publishes global app lifecycle events
         lazy var appLifecyclePublisher: AppLifecyclePublishing = ApplicationLifecyclePublisher.shared
         // publishes global screen view events (UIViewController.viewDidAppear)

PostHog/PostHogConfig.swift

@@ -54,6 +54,17 @@ public typealias BeforeSendBlock = (PostHogEvent) -> PostHogEvent?
 
     @objc public var captureApplicationLifecycleEvents: Bool = true
     @objc public var captureScreenViews: Bool = true
+
+    /// Enable method swizzling for SDK functionality that depends on it
+    ///
+    /// When disabled, functionality that require swizzling (like autocapture, screen views, session replay, surveys) will not be installed.
+    ///
+    /// Note: Disabling swizzling will limit session rotation logic to only detect application open and background events.
+    /// Session rotation will still work, just with reduced granularity for detecting user activity.
+    ///
+    /// Default: true
+    @objc public var enableSwizzling: Bool = true
+
     #if os(iOS) || targetEnvironment(macCatalyst)
         /// Enable autocapture for iOS
         /// Default: false

PostHog/PostHogIntegration.swift

@@ -7,6 +7,14 @@
 import Foundation
 
 protocol PostHogIntegration {
+    /**
+     * Indicates whether this integration requires method swizzling to function.
+     *
+     * When `enableSwizzling` is set to `false` in PostHogConfig, integrations
+     * that return `true` for this property will be skipped during installation.
+     */
+    var requiresSwizzling: Bool { get }
+
     /**
      * Installs and initializes the integration with a PostHogSDK instance.
      *

PostHog/PostHogSDK.swift

@@ -46,6 +46,7 @@ let maxRetryDelay = 30.0
     private var context: PostHogContext?
     private static var apiKeys = Set<String>()
     private var installedIntegrations: [PostHogIntegration] = []
+    let sessionManager = PostHogSessionManager()
 
     #if os(iOS)
         private weak var replayIntegration: PostHogReplayIntegration?
@@ -136,7 +137,9 @@ let maxRetryDelay = 30.0
             replayQueue?.start(disableReachabilityForTesting: config.disableReachabilityForTesting,
                                disableQueueTimerForTesting: config.disableQueueTimerForTesting)
 
-            PostHogSessionManager.shared.startSession()
+            // Create session manager instance for this PostHogSDK instance
+            sessionManager.setup(config: config)
+            sessionManager.startSession()
 
             if !config.optOut {
                 // don't install integrations if in opt-out state
@@ -170,23 +173,23 @@ let maxRetryDelay = 30.0
             return nil
         }
 
-        return PostHogSessionManager.shared.getSessionId(readOnly: true)
+        return sessionManager.getSessionId(readOnly: true)
     }
 
     @objc public func startSession() {
         if !isEnabled() {
             return
         }
 
-        PostHogSessionManager.shared.startSession()
+        sessionManager.startSession()
     }
 
     @objc public func endSession() {
         if !isEnabled() {
             return
         }
 
-        PostHogSessionManager.shared.endSession()
+        sessionManager.endSession()
     }
 
     // EVENT CAPTURE
@@ -303,7 +306,7 @@ let maxRetryDelay = 30.0
         // if not present, get a current or new session id at event timestamp
         let propSessionId = properties?["$session_id"] as? String
         let sessionId: String? = propSessionId.isNilOrEmpty
-            ? PostHogSessionManager.shared.getSessionId(at: timestamp ?? now())
+            ? sessionManager.getSessionId(at: timestamp ?? now())
             : propSessionId
 
         if let sessionId {
@@ -351,7 +354,7 @@ let maxRetryDelay = 30.0
         flagCallReportedLock.withLock {
             flagCallReported.removeAll()
         }
-        PostHogSessionManager.shared.resetSession()
+        sessionManager.reset()
 
         // Clear person and group properties for flags
         remoteConfig?.resetPersonPropertiesForFlags()
@@ -1270,7 +1273,7 @@ let maxRetryDelay = 30.0
                 flagCallReported.removeAll()
             }
             context = nil
-            PostHogSessionManager.shared.endSession()
+            sessionManager.endSession()
             toggleHedgeLog(false)
 
             uninstallIntegrations()
@@ -1328,8 +1331,8 @@ let maxRetryDelay = 30.0
             }
 
             let sessionId = resumeCurrent
-                ? PostHogSessionManager.shared.getSessionId()
-                : PostHogSessionManager.shared.getNextSessionId()
+                ? sessionManager.getSessionId()
+                : sessionManager.getNextSessionId()
 
             guard let sessionId else {
                 return hedgeLog("Could not start recording. Missing session id.")
@@ -1375,7 +1378,7 @@ let maxRetryDelay = 30.0
             }
 
             return replayIntegration.isActive()
-                && !PostHogSessionManager.shared.getSessionId(readOnly: true).isNilOrEmpty
+                && !sessionManager.getSessionId(readOnly: true).isNilOrEmpty
                 && remoteConfig.isSessionReplayFlagActive()
         }
     #endif
@@ -1396,6 +1399,12 @@ let maxRetryDelay = 30.0
         var installed: [PostHogIntegration] = []
 
         for integration in integrations {
+            // Skip integrations that require swizzling when swizzling is disabled
+            if integration.requiresSwizzling, !config.enableSwizzling {
+                hedgeLog("Integration \(type(of: integration)) skipped. Integration requires swizzling but enableSwizzling is disabled in config")
+                continue
+            }
+
             do {
                 try integration.install(self)
                 installed.append(integration)
@@ -1469,6 +1478,10 @@ let maxRetryDelay = 30.0
             }
         #endif
 
+        func getSessionManager() -> PostHogSessionManager? {
+            sessionManager
+        }
+
         func getAppLifeCycleIntegration() -> PostHogAppLifeCycleIntegration? {
             installedIntegrations.compactMap {
                 $0 as? PostHogAppLifeCycleIntegration

PostHog/PostHogSessionManager.swift

@@ -21,16 +21,31 @@ import Foundation
     }
 
     @objc public static var shared: PostHogSessionManager {
-        DI.main.sessionManager
+        PostHogSDK.shared.sessionManager
     }
 
-    // Private initializer to prevent multiple instances
+    private var config: PostHogConfig?
+
     override init() {
         super.init()
+    }
+
+    func setup(config: PostHogConfig) {
+        self.config = config
+        didBecomeActiveToken = nil
+        didEnterBackgroundToken = nil
+        applicationEventToken = nil
         registerNotifications()
         registerApplicationSendEvent()
     }
 
+    func reset() {
+        resetSession()
+        didBecomeActiveToken = nil
+        didEnterBackgroundToken = nil
+        applicationEventToken = nil
+    }
+
     private let queue = DispatchQueue(label: "com.posthog.PostHogSessionManager", target: .global(qos: .utility))
     private var sessionId: String?
     private var sessionStartTimestamp: TimeInterval?
@@ -237,8 +252,10 @@ import Foundation
 
     private func registerApplicationSendEvent() {
         #if os(iOS) || os(tvOS)
-            let applicationEventPublisher = DI.main.applicationEventPublisher
-            applicationEventToken = applicationEventPublisher.onApplicationEvent { [weak self] _, _ in
+            guard let config, config.enableSwizzling else {
+                return
+            }
+            applicationEventToken = DI.main.applicationEventPublisher.onApplicationEvent { [weak self] _, _ in
                 // update "last active" session
                 // we want to keep track of the idle time, so we need to maintain a timestamp on the last interactions of the user with the app. UIEvents are a good place to do so since it means that the user is actively interacting with the app (e.g not just noise background activity)
                 self?.queue.async {

PostHog/Replay/Plugins/Console Logs/PostHogSessionReplayConsoleLogsPlugin.swift

@@ -49,7 +49,7 @@
                 isActive,
                 let postHog,
                 postHog.isSessionReplayActive(),
-                let sessionId = PostHogSessionManager.shared.getSessionId(at: output.timestamp)
+                let sessionId = postHog.sessionManager.getSessionId(at: output.timestamp)
             else {
                 return
             }

PostHog/Replay/Plugins/Network/PostHogSessionReplayNetworkPlugin.swift

@@ -19,7 +19,10 @@
             do {
                 sessionSwizzler = try URLSessionSwizzler(
                     shouldCapture: shouldCaptureNetworkSample,
-                    onCapture: handleNetworkSample
+                    onCapture: handleNetworkSample,
+                    getSessionId: { [weak self] date in
+                        self?.postHog?.sessionManager.getSessionId(at: date)
+                    }
                 )
                 sessionSwizzler?.swizzle()
                 hedgeLog("[Session Replay] Network telemetry plugin started")

PostHog/Replay/Plugins/Network/URLSessionExtension.swift

@@ -26,7 +26,7 @@
             let timestamp = Date()
             let startMillis = getMonotonicTimeInMilliseconds()
             var endMillis: UInt64?
-            let sessionId = PostHogSessionManager.shared.getSessionId(at: timestamp)
+            let sessionId = postHog?.sessionManager.getSessionId(at: timestamp)
             do {
                 let (data, response) = try await action()
                 endMillis = getMonotonicTimeInMilliseconds()
@@ -57,7 +57,7 @@
             let timestamp = Date()
             let startMillis = getMonotonicTimeInMilliseconds()
             var endMillis: UInt64?
-            let sessionId = PostHogSessionManager.shared.getSessionId(at: timestamp)
+            let sessionId = postHog?.sessionManager.getSessionId(at: timestamp)
             do {
                 let (url, response) = try await action()
                 endMillis = getMonotonicTimeInMilliseconds()

PostHog/Replay/Plugins/Network/URLSessionInterceptor.swift

@@ -12,10 +12,12 @@
         private let tasksLock = NSLock()
         private let shouldCapture: () -> Bool
         private let onCapture: (NetworkSample) -> Void
+        private let getSessionId: (Date) -> String?
 
-        init(shouldCapture: @escaping () -> Bool, onCapture: @escaping (NetworkSample) -> Void) {
+        init(shouldCapture: @escaping () -> Bool, onCapture: @escaping (NetworkSample) -> Void, getSessionId: @escaping (Date) -> String?) {
             self.shouldCapture = shouldCapture
             self.onCapture = onCapture
+            self.getSessionId = getSessionId
         }
 
         /// An internal queue for synchronising the access to `samplesByTask`.
@@ -42,7 +44,7 @@
 
             let date = now()
 
-            guard let sessionId = PostHogSessionManager.shared.getSessionId(at: date) else {
+            guard let sessionId = getSessionId(date) else {
                 return
             }
 

PostHog/Replay/Plugins/Network/URLSessionSwizzler.swift

@@ -25,10 +25,11 @@
 
         private var hasSwizzled = false
 
-        init(shouldCapture: @escaping () -> Bool, onCapture: @escaping (NetworkSample) -> Void) throws {
+        init(shouldCapture: @escaping () -> Bool, onCapture: @escaping (NetworkSample) -> Void, getSessionId: @escaping (Date) -> String?) throws {
             interceptor = URLSessionInterceptor(
                 shouldCapture: shouldCapture,
-                onCapture: onCapture
+                onCapture: onCapture,
+                getSessionId: getSessionId
             )
 
             dataTaskWithURLAndCompletion = try DataTaskWithURLAndCompletion.build(interceptor: interceptor)

PostHog/Replay/PostHogReplayIntegration.swift

@@ -14,6 +14,8 @@
     import WebKit
 
     class PostHogReplayIntegration: PostHogIntegration {
+        var requiresSwizzling: Bool { true }
+
         private static var integrationInstalledLock = NSLock()
         private static var integrationInstalled = false
 
@@ -140,7 +142,7 @@
 
             isEnabled = true
             // reset views when session id changes (or is cleared) so we can re-send new metadata (or full snapshot in the future)
-            PostHogSessionManager.shared.onSessionIdChanged = { [weak self] in
+            postHog.sessionManager.onSessionIdChanged = { [weak self] in
                 self?.resetViews()
             }
 
@@ -183,7 +185,7 @@
             guard isEnabled else { return }
             isEnabled = false
             resetViews()
-            PostHogSessionManager.shared.onSessionIdChanged = {}
+            postHog?.sessionManager.onSessionIdChanged = {}
 
             // stop listening to `UIApplication.sendEvent`
             applicationEventToken = nil
@@ -249,7 +251,7 @@
 
             PostHogReplayIntegration.dispatchQueue.async { [touchInfo, weak postHog = postHog] in
                 // always make sure we have a fresh session id as early as possible
-                guard let sessionId = PostHogSessionManager.shared.getSessionId(at: date) else {
+                guard let sessionId = postHog?.sessionManager.getSessionId(at: date) else {
                     return
                 }
 
@@ -341,7 +343,7 @@
 
             PostHogReplayIntegration.dispatchQueue.async {
                 // always make sure we have a fresh session id at correct timestamp
-                guard let sessionId = PostHogSessionManager.shared.getSessionId(at: timestampDate) else {
+                guard let sessionId = postHog.sessionManager.getSessionId(at: timestampDate) else {
                     return
                 }
 

PostHog/Screen Views/PostHogScreenViewIntegration.swift

@@ -8,6 +8,8 @@
 import Foundation
 
 final class PostHogScreenViewIntegration: PostHogIntegration {
+    var requiresSwizzling: Bool { true }
+
     private static var integrationInstalledLock = NSLock()
     private static var integrationInstalled = false
 

PostHog/Surveys/PostHogSurveyIntegration.swift

@@ -13,6 +13,8 @@
     #endif
 
     final class PostHogSurveyIntegration: PostHogIntegration {
+        var requiresSwizzling: Bool { true }
+
         private static var integrationInstalledLock = NSLock()
         private static var integrationInstalled = false
 

PostHogTests/PostHogAutocaptureIntegrationSpec.swift

@@ -36,7 +36,7 @@ import Quick
                 server.stop()
                 server = nil
                 integration.stop()
-                PostHogSessionManager.shared.endSession {}
+                posthog.endSession()
                 posthog.close()
                 deleteSafely(applicationSupportDirectoryURL())
             }