Fixed a number of sync issues I noticed

ios/Ascently/Models/BackupFormat.swift

@@ -20,7 +20,6 @@ struct ClimbDataBackup: Codable {
     let problems: [BackupProblem]
     let sessions: [BackupClimbSession]
     let attempts: [BackupAttempt]
-    let deletedItems: [DeletedItem]
 
     init(
         exportedAt: String,
@@ -29,8 +28,7 @@ struct ClimbDataBackup: Codable {
         gyms: [BackupGym],
         problems: [BackupProblem],
         sessions: [BackupClimbSession],
-        attempts: [BackupAttempt],
-        deletedItems: [DeletedItem] = []
+        attempts: [BackupAttempt]
     ) {
         self.exportedAt = exportedAt
         self.version = version
@@ -39,7 +37,6 @@ struct ClimbDataBackup: Codable {
         self.problems = problems
         self.sessions = sessions
         self.attempts = attempts
-        self.deletedItems = deletedItems
     }
 }
 
@@ -52,6 +49,7 @@ struct BackupGym: Codable {
     let difficultySystems: [DifficultySystem]
     let customDifficultyGrades: [String]
     let notes: String?
+    let isDeleted: Bool?
     let createdAt: String
     let updatedAt: String
 
@@ -64,6 +62,8 @@ struct BackupGym: Codable {
         self.customDifficultyGrades = gym.customDifficultyGrades
         self.notes = gym.notes
 
+        self.isDeleted = false // Default to false until model is updated
+
         let formatter = ISO8601DateFormatter()
         formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
         self.createdAt = formatter.string(from: gym.createdAt)
@@ -78,6 +78,7 @@ struct BackupGym: Codable {
         difficultySystems: [DifficultySystem],
         customDifficultyGrades: [String] = [],
         notes: String?,
+        isDeleted: Bool = false,
         createdAt: String,
         updatedAt: String
     ) {
@@ -88,6 +89,7 @@ struct BackupGym: Codable {
         self.difficultySystems = difficultySystems
         self.customDifficultyGrades = customDifficultyGrades
         self.notes = notes
+        self.isDeleted = isDeleted
         self.createdAt = createdAt
         self.updatedAt = updatedAt
     }
@@ -115,6 +117,25 @@ struct BackupGym: Codable {
             updatedAt: updatedDate
         )
     }
+
+    static func createTombstone(id: String, deletedAt: Date) -> BackupGym {
+        let formatter = ISO8601DateFormatter()
+        formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
+        let dateString = formatter.string(from: deletedAt)
+
+        return BackupGym(
+            id: id,
+            name: "DELETED",
+            location: nil,
+            supportedClimbTypes: [],
+            difficultySystems: [],
+            customDifficultyGrades: [],
+            notes: nil,
+            isDeleted: true,
+            createdAt: dateString,
+            updatedAt: dateString
+        )
+    }
 }
 
 // Platform-neutral problem representation for backup/restore
@@ -131,6 +152,7 @@ struct BackupProblem: Codable {
     let isActive: Bool
     let dateSet: String?  // ISO 8601 format
     let notes: String?
+    let isDeleted: Bool?
     let createdAt: String
     let updatedAt: String
 
@@ -146,6 +168,7 @@ struct BackupProblem: Codable {
         self.imagePaths = problem.imagePaths.isEmpty ? nil : problem.imagePaths
         self.isActive = problem.isActive
         self.notes = problem.notes
+        self.isDeleted = false // Default to false until model is updated
 
         let formatter = ISO8601DateFormatter()
         formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
@@ -167,6 +190,7 @@ struct BackupProblem: Codable {
         isActive: Bool,
         dateSet: String?,
         notes: String?,
+        isDeleted: Bool = false,
         createdAt: String,
         updatedAt: String
     ) {
@@ -182,6 +206,7 @@ struct BackupProblem: Codable {
         self.isActive = isActive
         self.dateSet = dateSet
         self.notes = notes
+        self.isDeleted = isDeleted
         self.createdAt = createdAt
         self.updatedAt = updatedAt
     }
@@ -232,10 +257,35 @@ struct BackupProblem: Codable {
             isActive: self.isActive,
             dateSet: self.dateSet,
             notes: self.notes,
+            isDeleted: self.isDeleted ?? false,
             createdAt: self.createdAt,
             updatedAt: self.updatedAt
         )
     }
+
+    static func createTombstone(id: String, gymId: String = UUID().uuidString, deletedAt: Date) -> BackupProblem {
+        let formatter = ISO8601DateFormatter()
+        formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
+        let dateString = formatter.string(from: deletedAt)
+
+        return BackupProblem(
+            id: id,
+            gymId: gymId,
+            name: "DELETED",
+            description: nil,
+            climbType: ClimbType.allCases.first!,
+            difficulty: DifficultyGrade(system: DifficultySystem.allCases.first!, grade: "0"),
+            tags: [],
+            location: nil,
+            imagePaths: nil,
+            isActive: false,
+            dateSet: nil,
+            notes: nil,
+            isDeleted: true,
+            createdAt: dateString,
+            updatedAt: dateString
+        )
+    }
 }
 
 // Platform-neutral climb session representation for backup/restore
@@ -248,6 +298,7 @@ struct BackupClimbSession: Codable {
     let duration: Int64?  // Duration in seconds
     let status: SessionStatus
     let notes: String?
+    let isDeleted: Bool?
     let createdAt: String
     let updatedAt: String
 
@@ -256,6 +307,7 @@ struct BackupClimbSession: Codable {
         self.gymId = session.gymId.uuidString
         self.status = session.status
         self.notes = session.notes
+        self.isDeleted = false // Default to false until model is updated
 
         let formatter = ISO8601DateFormatter()
         formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
@@ -276,6 +328,7 @@ struct BackupClimbSession: Codable {
         duration: Int64?,
         status: SessionStatus,
         notes: String?,
+        isDeleted: Bool = false,
         createdAt: String,
         updatedAt: String
     ) {
@@ -287,6 +340,7 @@ struct BackupClimbSession: Codable {
         self.duration = duration
         self.status = status
         self.notes = notes
+        self.isDeleted = isDeleted
         self.createdAt = createdAt
         self.updatedAt = updatedAt
     }
@@ -321,6 +375,26 @@ struct BackupClimbSession: Codable {
             updatedAt: updatedDate
         )
     }
+
+    static func createTombstone(id: String, gymId: String = UUID().uuidString, deletedAt: Date) -> BackupClimbSession {
+        let formatter = ISO8601DateFormatter()
+        formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
+        let dateString = formatter.string(from: deletedAt)
+
+        return BackupClimbSession(
+            id: id,
+            gymId: gymId,
+            date: dateString,
+            startTime: nil,
+            endTime: nil,
+            duration: nil,
+            status: .finished,
+            notes: nil,
+            isDeleted: true,
+            createdAt: dateString,
+            updatedAt: dateString
+        )
+    }
 }
 
 // Platform-neutral attempt representation for backup/restore
@@ -334,6 +408,7 @@ struct BackupAttempt: Codable {
     let duration: Int64?  // Duration in seconds
     let restTime: Int64?  // Rest time in seconds
     let timestamp: String
+    let isDeleted: Bool?
     let createdAt: String
     let updatedAt: String?
 
@@ -346,6 +421,7 @@ struct BackupAttempt: Codable {
         self.notes = attempt.notes
         self.duration = attempt.duration.map { Int64($0) }
         self.restTime = attempt.restTime.map { Int64($0) }
+        self.isDeleted = false // Default to false until model is updated
 
         let formatter = ISO8601DateFormatter()
         formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
@@ -364,6 +440,7 @@ struct BackupAttempt: Codable {
         duration: Int64?,
         restTime: Int64?,
         timestamp: String,
+        isDeleted: Bool = false,
         createdAt: String,
         updatedAt: String?
     ) {
@@ -376,6 +453,7 @@ struct BackupAttempt: Codable {
         self.duration = duration
         self.restTime = restTime
         self.timestamp = timestamp
+        self.isDeleted = isDeleted
         self.createdAt = createdAt
         self.updatedAt = updatedAt
     }
@@ -412,6 +490,27 @@ struct BackupAttempt: Codable {
             updatedAt: updatedDate
         )
     }
+
+    static func createTombstone(id: String, sessionId: String = UUID().uuidString, problemId: String = UUID().uuidString, deletedAt: Date) -> BackupAttempt {
+        let formatter = ISO8601DateFormatter()
+        formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
+        let dateString = formatter.string(from: deletedAt)
+
+        return BackupAttempt(
+            id: id,
+            sessionId: sessionId,
+            problemId: problemId,
+            result: AttemptResult.allCases.first!,
+            highestHold: nil,
+            notes: nil,
+            duration: nil,
+            restTime: nil,
+            timestamp: dateString,
+            isDeleted: true,
+            createdAt: dateString,
+            updatedAt: dateString
+        )
+    }
 }
 
 // MARK: - Backup Format Errors

ios/Ascently/Models/DeltaSyncFormat.swift

@@ -13,7 +13,6 @@ struct DeltaSyncRequest: Codable {
     let problems: [BackupProblem]
     let sessions: [BackupClimbSession]
     let attempts: [BackupAttempt]
-    let deletedItems: [DeletedItem]
 }
 
 struct DeltaSyncResponse: Codable {
@@ -22,5 +21,4 @@ struct DeltaSyncResponse: Codable {
     let problems: [BackupProblem]
     let sessions: [BackupClimbSession]
     let attempts: [BackupAttempt]
-    let deletedItems: [DeletedItem]
 }

ios/Ascently/Views/SettingsView.swift

@@ -6,6 +6,7 @@ import UniformTypeIdentifiers
 enum SheetType {
     case export(Data)
     case importData
+    case syncSettings
 }
 
 struct SettingsView: View {
@@ -16,7 +17,7 @@ struct SettingsView: View {
     var body: some View {
         NavigationStack {
             List {
-                SyncSection()
+                SyncSection(activeSheet: $activeSheet)
                     .environmentObject(dataManager.syncService)
 
                 HealthKitSection()
@@ -67,6 +68,9 @@ struct SettingsView: View {
                     ExportDataView(data: data)
                 case .importData:
                     ImportDataView()
+                case .syncSettings:
+                    SyncSettingsView()
+                        .environmentObject(dataManager.syncService)
                 }
             }
         }
@@ -78,6 +82,7 @@ extension SheetType: Identifiable {
         switch self {
         case .export: return "export"
         case .importData: return "import"
+        case .syncSettings: return "sync_settings"
         }
     }
 }
@@ -526,7 +531,7 @@ struct SyncSection: View {
     @EnvironmentObject var syncService: SyncService
     @EnvironmentObject var dataManager: ClimbingDataManager
     @EnvironmentObject var themeManager: ThemeManager
-    @State private var showingSyncSettings = false
+    @Binding var activeSheet: SheetType?
     @State private var showingDisconnectAlert = false
 
     private static let logTag = "SyncSection"
@@ -567,7 +572,7 @@ struct SyncSection: View {
 
             // Configure Server
             Button(action: {
-                showingSyncSettings = true
+                activeSheet = .syncSettings
             }) {
                 HStack {
                     Image(systemName: "gear")
@@ -657,10 +662,6 @@ struct SyncSection: View {
                 }
             }
         }
-        .sheet(isPresented: $showingSyncSettings) {
-            SyncSettingsView()
-                .environmentObject(syncService)
-        }
         .alert("Disconnect from Server", isPresented: $showingDisconnectAlert) {
             Button("Cancel", role: .cancel) {}
             Button("Disconnect", role: .destructive) {
@@ -702,24 +703,14 @@ struct SyncSettingsView: View {
         NavigationStack {
             Form {
                 Section {
-                    TextField("Server URL", text: $serverURL)
-                        .textFieldStyle(.roundedBorder)
+                    TextField("Server URL", text: $serverURL, prompt: Text("http://your-server:8080"))
                         .keyboardType(.URL)
                         .autocapitalization(.none)
                         .disableAutocorrection(true)
-                        .placeholder(when: serverURL.isEmpty) {
-                            Text("http://your-server:8080")
-                                .foregroundColor(.secondary)
-                        }
 
-                    TextField("Auth Token", text: $authToken)
-                        .textFieldStyle(.roundedBorder)
+                    TextField("Auth Token", text: $authToken, prompt: Text("your-secret-token"))
                         .autocapitalization(.none)
                         .disableAutocorrection(true)
-                        .placeholder(when: authToken.isEmpty) {
-                            Text("your-secret-token")
-                                .foregroundColor(.secondary)
-                        }
                 } header: {
                     Text("Server Configuration")
                 } footer: {
@@ -845,37 +836,34 @@ struct SyncSettingsView: View {
         let originalURL = syncService.serverURL
         let originalToken = syncService.authToken
 
-        Task {
+        Task { @MainActor in
             do {
                 // Ensure we are using the server provider
-                await MainActor.run {
-                    if syncService.providerType != .server {
-                        syncService.providerType = .server
-                    }
+                if syncService.providerType != .server {
+                    syncService.providerType = .server
                 }
 
                 // Temporarily set the values for testing
                 syncService.serverURL = testURL
                 syncService.authToken = testToken
 
+                // Explicitly sync UserDefaults to ensure immediate availability
+                UserDefaults.standard.synchronize()
+
                 try await syncService.testConnection()
 
-                await MainActor.run {
-                    isTesting = false
-                    testResultMessage =
-                        "Connection successful! You can now save and sync your data."
-                    showingTestResult = true
-                }
+                isTesting = false
+                testResultMessage =
+                    "Connection successful! You can now save and sync your data."
+                showingTestResult = true
             } catch {
                 // Restore original values if test failed
                 syncService.serverURL = originalURL
                 syncService.authToken = originalToken
 
-                await MainActor.run {
-                    isTesting = false
-                    testResultMessage = "Connection failed: \(error.localizedDescription)"
-                    showingTestResult = true
-                }
+                isTesting = false
+                testResultMessage = "Connection failed: \(error.localizedDescription)"
+                showingTestResult = true
             }
         }
     }

sync/main.go

@@ -13,7 +13,7 @@ import (
 	"time"
 )
 
-const VERSION = "2.3.0"
+const VERSION = "2.4.0"
 
 func min(a, b int) int {
 	if a < b {
@@ -22,12 +22,6 @@ func min(a, b int) int {
 	return b
 }
 
-type DeletedItem struct {
-	ID        string `json:"id"`
-	Type      string `json:"type"`
-	DeletedAt string `json:"deletedAt"`
-}
-
 type ClimbDataBackup struct {
 	ExportedAt    string               `json:"exportedAt"`
 	Version       string               `json:"version"`
@@ -36,7 +30,6 @@ type ClimbDataBackup struct {
 	Problems      []BackupProblem      `json:"problems"`
 	Sessions      []BackupClimbSession `json:"sessions"`
 	Attempts      []BackupAttempt      `json:"attempts"`
-	DeletedItems  []DeletedItem        `json:"deletedItems"`
 }
 
 type DeltaSyncRequest struct {
@@ -45,16 +38,14 @@ type DeltaSyncRequest struct {
 	Problems     []BackupProblem      `json:"problems"`
 	Sessions     []BackupClimbSession `json:"sessions"`
 	Attempts     []BackupAttempt      `json:"attempts"`
-	DeletedItems []DeletedItem        `json:"deletedItems"`
 }
 
 type DeltaSyncResponse struct {
-	ServerTime   string               `json:"serverTime"`
-	Gyms         []BackupGym          `json:"gyms"`
-	Problems     []BackupProblem      `json:"problems"`
-	Sessions     []BackupClimbSession `json:"sessions"`
-	Attempts     []BackupAttempt      `json:"attempts"`
-	DeletedItems []DeletedItem        `json:"deletedItems"`
+	ServerTime string               `json:"serverTime"`
+	Gyms       []BackupGym          `json:"gyms"`
+	Problems   []BackupProblem      `json:"problems"`
+	Sessions   []BackupClimbSession `json:"sessions"`
+	Attempts   []BackupAttempt      `json:"attempts"`
 }
 
 type BackupGym struct {
@@ -65,6 +56,7 @@ type BackupGym struct {
 	DifficultySystems      []string `json:"difficultySystems"`
 	CustomDifficultyGrades []string `json:"customDifficultyGrades"`
 	Notes                  *string  `json:"notes,omitempty"`
+	IsDeleted              bool     `json:"isDeleted"`
 	CreatedAt              string   `json:"createdAt"`
 	UpdatedAt              string   `json:"updatedAt"`
 }
@@ -82,6 +74,7 @@ type BackupProblem struct {
 	IsActive    bool            `json:"isActive"`
 	DateSet     *string         `json:"dateSet,omitempty"`
 	Notes       *string         `json:"notes,omitempty"`
+	IsDeleted   bool            `json:"isDeleted"`
 	CreatedAt   string          `json:"createdAt"`
 	UpdatedAt   string          `json:"updatedAt"`
 }
@@ -101,6 +94,7 @@ type BackupClimbSession struct {
 	Duration  *int64  `json:"duration,omitempty"`
 	Status    string  `json:"status"`
 	Notes     *string `json:"notes,omitempty"`
+	IsDeleted bool    `json:"isDeleted"`
 	CreatedAt string  `json:"createdAt"`
 	UpdatedAt string  `json:"updatedAt"`
 }
@@ -115,7 +109,9 @@ type BackupAttempt struct {
 	Duration    *int64  `json:"duration,omitempty"`
 	RestTime    *int64  `json:"restTime,omitempty"`
 	Timestamp   string  `json:"timestamp"`
+	IsDeleted   bool    `json:"isDeleted"`
 	CreatedAt   string  `json:"createdAt"`
+	UpdatedAt   *string `json:"updatedAt,omitempty"`
 }
 
 type SyncServer struct {
@@ -147,7 +143,6 @@ func (s *SyncServer) loadData() (*ClimbDataBackup, error) {
 			Problems:      []BackupProblem{},
 			Sessions:      []BackupClimbSession{},
 			Attempts:      []BackupAttempt{},
-			DeletedItems:  []DeletedItem{},
 		}, nil
 	}
 
@@ -158,7 +153,18 @@ func (s *SyncServer) loadData() (*ClimbDataBackup, error) {
 	}
 
 	log.Printf("Read %d bytes from data file", len(data))
-	log.Printf("File content preview: %s", string(data[:min(200, len(data))]))
+	// Basic check to see if we have JSON content
+	if len(data) == 0 {
+		return &ClimbDataBackup{
+			ExportedAt:    time.Now().UTC().Format(time.RFC3339),
+			Version:       "2.0",
+			FormatVersion: "2.0",
+			Gyms:          []BackupGym{},
+			Problems:      []BackupProblem{},
+			Sessions:      []BackupClimbSession{},
+			Attempts:      []BackupAttempt{},
+		}, nil
+	}
 
 	var backup ClimbDataBackup
 	if err := json.Unmarshal(data, &backup); err != nil {
@@ -250,7 +256,18 @@ func (s *SyncServer) mergeAttempts(existing []BackupAttempt, updates []BackupAtt
 
 	for _, attempt := range updates {
 		if existingAttempt, exists := attemptMap[attempt.ID]; exists {
-			if attempt.CreatedAt >= existingAttempt.CreatedAt {
+			// Resolve update time for comparison
+			updateTime := attempt.CreatedAt
+			if attempt.UpdatedAt != nil {
+				updateTime = *attempt.UpdatedAt
+			}
+
+			existingUpdateTime := existingAttempt.CreatedAt
+			if existingAttempt.UpdatedAt != nil {
+				existingUpdateTime = *existingAttempt.UpdatedAt
+			}
+
+			if updateTime >= existingUpdateTime {
 				attemptMap[attempt.ID] = attempt
 			}
 		} else {
@@ -265,89 +282,6 @@ func (s *SyncServer) mergeAttempts(existing []BackupAttempt, updates []BackupAtt
 	return result
 }
 
-func (s *SyncServer) mergeDeletedItems(existing []DeletedItem, updates []DeletedItem) []DeletedItem {
-	deletedMap := make(map[string]DeletedItem)
-	for _, item := range existing {
-		key := item.Type + ":" + item.ID
-		deletedMap[key] = item
-	}
-
-	for _, item := range updates {
-		key := item.Type + ":" + item.ID
-		if existingItem, exists := deletedMap[key]; exists {
-			if item.DeletedAt >= existingItem.DeletedAt {
-				deletedMap[key] = item
-			}
-		} else {
-			deletedMap[key] = item
-		}
-	}
-
-	// Clean up tombstones older than 30 days to prevent unbounded growth
-	cutoffTime := time.Now().UTC().Add(-30 * 24 * time.Hour)
-	result := make([]DeletedItem, 0, len(deletedMap))
-	for _, item := range deletedMap {
-		deletedTime, err := time.Parse(time.RFC3339, item.DeletedAt)
-		if err == nil && deletedTime.Before(cutoffTime) {
-			log.Printf("Cleaning up old deletion record: type=%s, id=%s, deletedAt=%s",
-				item.Type, item.ID, item.DeletedAt)
-			continue
-		}
-		result = append(result, item)
-	}
-	return result
-}
-
-func (s *SyncServer) applyDeletions(backup *ClimbDataBackup, deletedItems []DeletedItem) {
-	deletedMap := make(map[string]map[string]bool)
-	for _, item := range deletedItems {
-		if deletedMap[item.Type] == nil {
-			deletedMap[item.Type] = make(map[string]bool)
-		}
-		deletedMap[item.Type][item.ID] = true
-	}
-
-	if deletedMap["gym"] != nil {
-		filtered := []BackupGym{}
-		for _, gym := range backup.Gyms {
-			if !deletedMap["gym"][gym.ID] {
-				filtered = append(filtered, gym)
-			}
-		}
-		backup.Gyms = filtered
-	}
-
-	if deletedMap["problem"] != nil {
-		filtered := []BackupProblem{}
-		for _, problem := range backup.Problems {
-			if !deletedMap["problem"][problem.ID] {
-				filtered = append(filtered, problem)
-			}
-		}
-		backup.Problems = filtered
-	}
-
-	if deletedMap["session"] != nil {
-		filtered := []BackupClimbSession{}
-		for _, session := range backup.Sessions {
-			if !deletedMap["session"][session.ID] {
-				filtered = append(filtered, session)
-			}
-		}
-		backup.Sessions = filtered
-	}
-
-	if deletedMap["attempt"] != nil {
-		filtered := []BackupAttempt{}
-		for _, attempt := range backup.Attempts {
-			if !deletedMap["attempt"][attempt.ID] {
-				filtered = append(filtered, attempt)
-			}
-		}
-		backup.Attempts = filtered
-	}
-}
-
 func (s *SyncServer) saveData(backup *ClimbDataBackup) error {
 	backup.ExportedAt = time.Now().UTC().Format(time.RFC3339)
 
@@ -383,6 +317,8 @@ func (s *SyncServer) handleGet(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+
+
 	log.Printf("Sending data to %s: gyms=%d, problems=%d, sessions=%d, attempts=%d",
 		r.RemoteAddr, len(backup.Gyms), len(backup.Problems), len(backup.Sessions), len(backup.Attempts))
 	w.Header().Set("Content-Type", "application/json")
@@ -527,11 +463,10 @@ func (s *SyncServer) handleDeltaSync(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	log.Printf("Delta sync from %s: lastSyncTime=%s, gyms=%d, problems=%d, sessions=%d, attempts=%d, deletedItems=%d",
+	log.Printf("Delta sync from %s: lastSyncTime=%s, gyms=%d, problems=%d, sessions=%d, attempts=%d",
 		r.RemoteAddr, deltaRequest.LastSyncTime,
 		len(deltaRequest.Gyms), len(deltaRequest.Problems),
-		len(deltaRequest.Sessions), len(deltaRequest.Attempts),
-		len(deltaRequest.DeletedItems))
+		len(deltaRequest.Sessions), len(deltaRequest.Attempts))
 
 	// Load current server data
 	serverBackup, err := s.loadData()
@@ -541,12 +476,9 @@ func (s *SyncServer) handleDeltaSync(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// Merge and apply deletions first to prevent resurrection
-	serverBackup.DeletedItems = s.mergeDeletedItems(serverBackup.DeletedItems, deltaRequest.DeletedItems)
-	s.applyDeletions(serverBackup, serverBackup.DeletedItems)
-	log.Printf("Applied deletions: total=%d deletion records", len(serverBackup.DeletedItems))
-
 	// Merge client changes into server data
+	// Note: We no longer need separate deletion handling as IsDeleted is part of the struct
+	// and handled by standard merge logic (latest timestamp wins)
 	serverBackup.Gyms = s.mergeGyms(serverBackup.Gyms, deltaRequest.Gyms)
 	serverBackup.Problems = s.mergeProblems(serverBackup.Problems, deltaRequest.Problems)
 	serverBackup.Sessions = s.mergeSessions(serverBackup.Sessions, deltaRequest.Sessions)
@@ -566,28 +498,17 @@ func (s *SyncServer) handleDeltaSync(w http.ResponseWriter, r *http.Request) {
 		log.Printf("Warning: Could not parse lastSyncTime '%s', sending all data", deltaRequest.LastSyncTime)
 	}
 
-	// Build deleted item lookup map
-	deletedItemMap := make(map[string]bool)
-	for _, item := range serverBackup.DeletedItems {
-		key := item.Type + ":" + item.ID
-		deletedItemMap[key] = true
-	}
-
 	// Prepare response with items modified since client's last sync
 	response := DeltaSyncResponse{
-		ServerTime:   time.Now().UTC().Format(time.RFC3339),
-		Gyms:         []BackupGym{},
-		Problems:     []BackupProblem{},
-		Sessions:     []BackupClimbSession{},
-		Attempts:     []BackupAttempt{},
-		DeletedItems: []DeletedItem{},
+		ServerTime: time.Now().UTC().Format(time.RFC3339),
+		Gyms:       []BackupGym{},
+		Problems:   []BackupProblem{},
+		Sessions:   []BackupClimbSession{},
+		Attempts:   []BackupAttempt{},
 	}
 
 	// Filter gyms modified after client's last sync
 	for _, gym := range serverBackup.Gyms {
-		if deletedItemMap["gym:"+gym.ID] {
-			continue
-		}
 		gymTime, err := time.Parse(time.RFC3339, gym.UpdatedAt)
 		if err == nil && gymTime.After(clientLastSync) {
 			response.Gyms = append(response.Gyms, gym)
@@ -596,9 +517,6 @@ func (s *SyncServer) handleDeltaSync(w http.ResponseWriter, r *http.Request) {
 
 	// Filter problems modified after client's last sync
 	for _, problem := range serverBackup.Problems {
-		if deletedItemMap["problem:"+problem.ID] {
-			continue
-		}
 		problemTime, err := time.Parse(time.RFC3339, problem.UpdatedAt)
 		if err == nil && problemTime.After(clientLastSync) {
 			response.Problems = append(response.Problems, problem)
@@ -607,39 +525,29 @@ func (s *SyncServer) handleDeltaSync(w http.ResponseWriter, r *http.Request) {
 
 	// Filter sessions modified after client's last sync
 	for _, session := range serverBackup.Sessions {
-		if deletedItemMap["session:"+session.ID] {
-			continue
-		}
 		sessionTime, err := time.Parse(time.RFC3339, session.UpdatedAt)
 		if err == nil && sessionTime.After(clientLastSync) {
 			response.Sessions = append(response.Sessions, session)
 		}
 	}
 
-	// Filter attempts created after client's last sync
+	// Filter attempts modified after client's last sync
 	for _, attempt := range serverBackup.Attempts {
-		if deletedItemMap["attempt:"+attempt.ID] {
-			continue
+		attemptTime := attempt.CreatedAt
+		if attempt.UpdatedAt != nil {
+			attemptTime = *attempt.UpdatedAt
 		}
-		attemptTime, err := time.Parse(time.RFC3339, attempt.CreatedAt)
-		if err == nil && attemptTime.After(clientLastSync) {
+
+		parsedTime, err := time.Parse(time.RFC3339, attemptTime)
+		if err == nil && parsedTime.After(clientLastSync) {
 			response.Attempts = append(response.Attempts, attempt)
 		}
 	}
 
-	// Filter deletions after client's last sync
-	for _, deletedItem := range serverBackup.DeletedItems {
-		deletedTime, err := time.Parse(time.RFC3339, deletedItem.DeletedAt)
-		if err == nil && deletedTime.After(clientLastSync) {
-			response.DeletedItems = append(response.DeletedItems, deletedItem)
-		}
-	}
-
-	log.Printf("Delta sync response to %s: gyms=%d, problems=%d, sessions=%d, attempts=%d, deletedItems=%d",
+	log.Printf("Delta sync response to %s: gyms=%d, problems=%d, sessions=%d, attempts=%d",
 		r.RemoteAddr,
 		len(response.Gyms), len(response.Problems),
-		len(response.Sessions), len(response.Attempts),
-		len(response.DeletedItems))
+		len(response.Sessions), len(response.Attempts))
 
 	w.Header().Set("Content-Type", "application/json")
 	json.NewEncoder(w).Encode(response)