Fix startup crash in sideloaded builds without iCloud entitlements

Sideloading tools re-sign the app with a team that cannot register the
iCloud.stream.yattee.app container, and CKContainer(identifier:) fatally
traps when the entitlement is missing. Detect availability by parsing
the embedded provisioning profile, skip creating any CloudKit objects
when the entitlement is absent, and show an explanation in iCloud
settings instead of the sync toggle.

Yattee/Localizable.xcstrings

@@ -12147,6 +12147,28 @@
         }
       }
     },
+    "settings.icloud.unavailable" : {
+      "comment" : "Label shown instead of the iCloud sync toggle when the app installation lacks iCloud entitlements",
+      "localizations" : {
+        "en" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "iCloud Sync Unavailable"
+          }
+        }
+      }
+    },
+    "settings.icloud.unavailable.footer" : {
+      "comment" : "Footer explaining why iCloud sync is unavailable in sideloaded installations",
+      "localizations" : {
+        "en" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "This copy of Yattee was installed without iCloud access, so sync is not available. iCloud sync requires installing the app from the App Store or TestFlight."
+          }
+        }
+      }
+    },
     "settings.icloud.update.message" : {
       "comment" : "Message explaining that newer app version is needed for some synced data",
       "localizations" : {

Yattee/Services/CloudKit/CloudKitAvailability.swift

@@ -0,0 +1,51 @@
+//
+//  CloudKitAvailability.swift
+//  Yattee
+//
+//  Detects whether the app was signed with the iCloud container entitlement.
+//
+
+import Foundation
+
+/// Sideloaded installs (AltStore, SideStore, Sideloadly, …) are re-signed by a
+/// team that cannot register `iCloud.stream.yattee.app` (container IDs are
+/// globally unique), so the iCloud entitlements are stripped or remapped.
+/// `CKContainer(identifier:)` fatally traps in that state, so the container
+/// must never be created when the entitlement is missing.
+enum CloudKitAvailability {
+    /// Whether CloudKit APIs may be used in this installation.
+    ///
+    /// Determined by parsing the embedded provisioning profile. Builds without
+    /// an embedded profile (App Store, TestFlight, simulator) always carry the
+    /// correct entitlements and are treated as available.
+    static let isAvailable: Bool = {
+        guard let entitlements = embeddedProvisioningEntitlements() else {
+            return true
+        }
+        let containers = entitlements["com.apple.developer.icloud-container-identifiers"] as? [String] ?? []
+        return containers.contains(AppIdentifiers.iCloudContainer)
+    }()
+
+    /// Extracts the entitlements dictionary from the embedded provisioning
+    /// profile — a CMS blob wrapping an XML property list.
+    private static func embeddedProvisioningEntitlements() -> [String: Any]? {
+        #if os(macOS)
+        let url = Bundle.main.bundleURL.appendingPathComponent("Contents/embedded.provisionprofile")
+        #else
+        guard let path = Bundle.main.path(forResource: "embedded", ofType: "mobileprovision") else { return nil }
+        let url = URL(fileURLWithPath: path)
+        #endif
+
+        guard let data = try? Data(contentsOf: url),
+              let start = data.range(of: Data("<?xml".utf8)),
+              let end = data.range(of: Data("</plist>".utf8), in: start.lowerBound..<data.endIndex),
+              let plist = try? PropertyListSerialization.propertyList(
+                  from: data.subdata(in: start.lowerBound..<end.upperBound),
+                  format: nil
+              ),
+              let profile = plist as? [String: Any]
+        else { return nil }
+
+        return profile["Entitlements"] as? [String: Any]
+    }
+}

Yattee/Services/CloudKit/CloudKitSyncEngine.swift

@@ -64,9 +64,14 @@ final class CloudKitSyncEngine: @unchecked Sendable {
 
     // MARK: - State
 
-    private let container: CKContainer
-    private let database: CKDatabase
-    private let zoneManager: CloudKitZoneManager
+    /// Whether CloudKit is usable in this installation. False when the app was
+    /// re-signed without the iCloud container entitlement (sideloading); all
+    /// sync functionality is disabled then and the CloudKit objects stay nil.
+    let isCloudKitAvailable = CloudKitAvailability.isAvailable
+
+    private let container: CKContainer?
+    private let database: CKDatabase?
+    private let zoneManager: CloudKitZoneManager?
     private var recordMapper: CloudKitRecordMapper
     private var conflictResolver: CloudKitConflictResolver
     private var syncEngine: CKSyncEngine?
@@ -232,12 +237,21 @@ final class CloudKitSyncEngine: @unchecked Sendable {
         self.settingsManager = settingsManager
         self.instancesManager = instancesManager
         
-        // Initialize CloudKit
-        self.container = CKContainer(identifier: AppIdentifiers.iCloudContainer)
-        self.database = container.privateCloudDatabase
-        
-        // Initialize zone manager
+        // Initialize CloudKit. CKContainer(identifier:) fatally traps when the
+        // entitlement is missing (re-signed/sideloaded builds), so it must not
+        // be constructed at all in that case.
+        if CloudKitAvailability.isAvailable {
+            let container = CKContainer(identifier: AppIdentifiers.iCloudContainer)
+            let database = container.privateCloudDatabase
+            self.container = container
+            self.database = database
             self.zoneManager = CloudKitZoneManager(database: database)
+        } else {
+            LoggingService.shared.logCloudKit("iCloud container entitlement missing (re-signed build) - CloudKit sync unavailable")
+            self.container = nil
+            self.database = nil
+            self.zoneManager = nil
+        }
         
         // Initialize with temporary zone (will be updated in setupSyncEngine)
         let tempZone = RecordType.createZone()
@@ -261,6 +275,10 @@ final class CloudKitSyncEngine: @unchecked Sendable {
 
     /// Enables CloudKit sync. Creates CKSyncEngine and starts syncing.
     func enable() async {
+        guard isCloudKitAvailable else {
+            LoggingService.shared.logCloudKit("CloudKit unavailable in this installation, cannot enable sync")
+            return
+        }
         guard syncEngine == nil else {
             LoggingService.shared.logCloudKit("Sync engine already enabled")
             return
@@ -312,6 +330,11 @@ final class CloudKitSyncEngine: @unchecked Sendable {
             return
         }
 
+        guard let container, let database, let zoneManager else {
+            LoggingService.shared.logCloudKit("CloudKit unavailable in this installation, skipping engine setup")
+            return
+        }
+
         do {
             // Check iCloud account status
             let status = try await container.accountStatus()
@@ -387,6 +410,7 @@ final class CloudKitSyncEngine: @unchecked Sendable {
     /// Checks if the iCloud account has changed and handles it by clearing sync state.
     /// - Returns: `true` if account changed and sync state was cleared, `false` otherwise.
     private func checkAndHandleAccountChange() async -> Bool {
+        guard let container else { return false }
         do {
             // Fetch the current user's record ID using async wrapper
             let currentUserRecordID = try await withCheckedThrowingContinuation { (continuation: CheckedContinuation<CKRecord.ID, Error>) in
@@ -1422,6 +1446,8 @@ final class CloudKitSyncEngine: @unchecked Sendable {
 
     /// Clear all sync state and reset. For testing/debugging only.
     func resetSync() async throws {
+        guard let zoneManager else { return }
+
         // Delete zone (and all records)
         try await zoneManager.deleteZone()
 
@@ -1449,6 +1475,7 @@ final class CloudKitSyncEngine: @unchecked Sendable {
     
     /// Refreshes the cached iCloud account status
     func refreshAccountStatus() async {
+        guard let container else { return }
         do {
             accountStatus = try await container.accountStatus()
         } catch {
@@ -1566,7 +1593,7 @@ final class CloudKitSyncEngine: @unchecked Sendable {
         case .zoneNotFound:
             LoggingService.shared.logCloudKit("Zone not found, recreating...")
             Task {
-                try? await zoneManager.createZoneIfNeeded()
+                try? await zoneManager?.createZoneIfNeeded()
                 await sync()
             }
             
@@ -1882,7 +1909,7 @@ extension CloudKitSyncEngine: CKSyncEngineDelegate {
             // Zone was deleted — recreate it and retry the save
             syncEngine?.state.add(pendingRecordZoneChanges: [.saveRecord(recordID)])
             Task {
-                try? await zoneManager.createZoneIfNeeded()
+                try? await zoneManager?.createZoneIfNeeded()
             }
             LoggingService.shared.logCloudKit("Zone missing for \(recordName), recreating and retrying")
 
@@ -1966,7 +1993,7 @@ extension CloudKitSyncEngine: CKSyncEngineDelegate {
         retryCount.removeAll()
 
         do {
-            try await zoneManager.createZoneIfNeeded()
+            try await zoneManager?.createZoneIfNeeded()
             await performInitialUpload()
         } catch {
             LoggingService.shared.logCloudKitError("Failed to recreate zone after remote deletion", error: error)

Yattee/Views/Settings/iCloudSettingsView.swift

@@ -58,6 +58,12 @@ struct iCloudSettingsView: View {
             }
             #endif
 
+            if cloudKitSync?.isCloudKitAvailable == false {
+                SettingsFormSection(footer: "settings.icloud.unavailable.footer") {
+                    Label(String(localized: "settings.icloud.unavailable"), systemImage: "icloud.slash")
+                        .foregroundStyle(.secondary)
+                }
+            } else {
                 SettingsFormSection(footer: "settings.icloud.footer") {
                     Toggle(isOn: Binding(
                         get: { settingsManager?.iCloudSyncEnabled ?? false },
@@ -78,6 +84,7 @@ struct iCloudSettingsView: View {
                     syncStatusSection
                 }
             }
+        }
         #if !os(tvOS)
         .navigationTitle(String(localized: "settings.icloud.title"))
         #endif