diff --git a/Sources/Services/ContainerIsolationService.swift b/Sources/Services/ContainerIsolationService.swift
index 85865ed..ca0e3e6 100644
--- a/Sources/Services/ContainerIsolationService.swift
+++ b/Sources/Services/ContainerIsolationService.swift
@@ -1,7 +1,7 @@
 import Foundation
 
 #if canImport(Containerization)
-import Containerization
+@preconcurrency import Containerization
 #endif
 
 /// Service for managing container-based isolation of GitHub Actions runners.
@@ -21,6 +21,7 @@ import Containerization
 /// - Mounted workspace directory
 /// - GitHub Actions runner environment
 @available(macOS 26.0, *)
+@MainActor
 class ContainerIsolationService {
     #if canImport(Containerization)
     // MARK: - Properties
@@ -103,12 +104,7 @@ class ContainerIsolationService {
         // Determine which container image to use
         let imageReference = config.containerImage ?? ContainerRunnerConfiguration.defaultRunnerImage
 
-        // Create container with specified configuration
-        let container = try await manager.create(
-            id,
-            reference: imageReference,
-            rootfsSizeInBytes: config.diskSizeInBytes
-        ) { containerConfig in
+        let configuration: @Sendable (inout LinuxContainer.Configuration) -> Void = { containerConfig in
             // Resource allocation
             containerConfig.cpus = config.cpuCount
             containerConfig.memoryInBytes = config.memoryInBytes
@@ -146,13 +142,19 @@ class ContainerIsolationService {
             // Set environment variables
             containerConfig.process.environmentVariables.append("RUNNER_ALLOW_RUNASROOT=1")
 
-            // Enable nested virtualization if requested
             if config.enableNestedVirtualization {
-                // Note: This may not be supported in all versions of the framework
-                // containerConfig.enableNestedVirtualization = true
+                // Reserved for framework support.
             }
         }
 
+        // Create container with specified configuration
+        let container = try await manager.create(
+            id,
+            reference: imageReference,
+            rootfsSizeInBytes: config.diskSizeInBytes,
+            configuration: configuration
+        )
+
         // Store mutated manager back
         self.containerManager = manager
 
diff --git a/Sources/Services/RunnerManager.swift b/Sources/Services/RunnerManager.swift
index 33f981b..51ebefe 100644
--- a/Sources/Services/RunnerManager.swift
+++ b/Sources/Services/RunnerManager.swift
@@ -9,6 +9,12 @@ import Containerization
 
 @MainActor
 class RunnerManager: ObservableObject {
+    enum LoginItemAction: Equatable {
+        case register
+        case unregister
+        case none
+    }
+
     private enum UpdateStatusMessages {
         static let defaultAutomaticChecks = "Checks GitHub releases on launch and once per day."
         static let alreadyChecking = "Update check already in progress."
@@ -96,7 +102,7 @@ class RunnerManager: ObservableObject {
         }
 
         reconcileRunnerStates()
-        syncLoginItem()
+        reconcileLoginItemSetting()
         startStatusPolling()
     }
 
@@ -352,32 +358,51 @@ class RunnerManager: ObservableObject {
 
     // MARK: - Login Item
 
-    /// Synchronize the macOS login item registration with current settings.
+    /// Reconcile the persisted setting with the current macOS login item state.
     ///
-    /// First reconciles the config with the actual OS state (in case the user toggled
-    /// the login item via System Settings), then registers or unregisters as needed.
+    /// This is intentionally only performed during initialization. A user change in
+    /// Mac Runner must be applied to macOS before the system state can be trusted;
+    /// otherwise enabling the toggle is immediately overwritten by the old state.
+    private func reconcileLoginItemSetting() {
+        let osEnabled = SMAppService.mainApp.status == .enabled
+        guard currentSettings.startOnLogin != osEnabled else { return }
+
+        currentSettings.startOnLogin = osEnabled
+        saveConfiguration()
+    }
+
+    /// Apply the current setting to the macOS login item registration.
     private func syncLoginItem() {
         let service = SMAppService.mainApp
-        let osEnabled = service.status == .enabled
-
-        // Reconcile: if OS state disagrees with config, trust the OS
-        if currentSettings.startOnLogin != osEnabled {
-            currentSettings.startOnLogin = osEnabled
-            saveConfiguration()
-        }
 
         do {
-            if currentSettings.startOnLogin {
-                if service.status != .enabled {
-                    try service.register()
-                }
-            } else {
-                if service.status == .enabled {
-                    try service.unregister()
-                }
+            switch Self.loginItemAction(
+                startOnLogin: currentSettings.startOnLogin,
+                isRegistered: service.status == .enabled
+            ) {
+            case .register:
+                try service.register()
+            case .unregister:
+                try service.unregister()
+            case .none:
+                break
             }
         } catch {
-            self.error = "Failed to update login item: \(error.localizedDescription)"
+            let loginItemError = "Failed to update login item: \(error.localizedDescription)"
+            currentSettings.startOnLogin = service.status == .enabled
+            saveConfiguration()
+            self.error = loginItemError
+        }
+    }
+
+    nonisolated static func loginItemAction(
+        startOnLogin: Bool,
+        isRegistered: Bool
+    ) -> LoginItemAction {
+        switch (startOnLogin, isRegistered) {
+        case (true, false): return .register
+        case (false, true): return .unregister
+        default: return .none
         }
     }
 
diff --git a/Tests/MacRunnerTests/MacRunnerTests.swift b/Tests/MacRunnerTests/MacRunnerTests.swift
index 7212747..cde6555 100644
--- a/Tests/MacRunnerTests/MacRunnerTests.swift
+++ b/Tests/MacRunnerTests/MacRunnerTests.swift
@@ -6,6 +6,20 @@ final class MacRunnerTests: XCTestCase {
         XCTAssertTrue(true)
     }
 
+    func testEnablingLaunchAtLoginRegistersWhenSystemItemIsDisabled() {
+        XCTAssertEqual(
+            RunnerManager.loginItemAction(startOnLogin: true, isRegistered: false),
+            .register
+        )
+    }
+
+    func testDisablingLaunchAtLoginUnregistersWhenSystemItemIsEnabled() {
+        XCTAssertEqual(
+            RunnerManager.loginItemAction(startOnLogin: false, isRegistered: true),
+            .unregister
+        )
+    }
+
     func testPreferredKernelPathPrefersBundledKernel() {
         let bundleURL = URL(fileURLWithPath: "/Applications/MacRunner.app/Contents/Resources")
         let appSupportURL = URL(fileURLWithPath: "/Users/test/Library/Application Support/MacRunner")
diff --git a/Tests/MacRunnerTests/UpdateCheckerTests.swift b/Tests/MacRunnerTests/UpdateCheckerTests.swift
index 817d15b..a524f84 100644
--- a/Tests/MacRunnerTests/UpdateCheckerTests.swift
+++ b/Tests/MacRunnerTests/UpdateCheckerTests.swift
@@ -97,7 +97,13 @@ final class UpdateCheckerTests: XCTestCase {
 
     func testHomebrewInstallDetectionUsesCellarPaths() {
         XCTAssertEqual(UpdateChecker.installSource(for: "/opt/homebrew/Cellar/mac-runner/1.2.3/Mac Runner.app"), .homebrewFormula)
-        XCTAssertEqual(UpdateChecker.installSource(for: "/Applications/Mac Runner.app"), .directDownload)
+        XCTAssertEqual(
+            UpdateChecker.installSource(
+                for: "/Applications/Mac Runner.app",
+                fileExists: { _ in false }
+            ),
+            .directDownload
+        )
     }
 
     func testHomebrewInstallDetectionUsesCaskReceipt() {