Fix duplicate messages after channel switch\n\n- Dedup on per-geohash append (skip if ID exists)\n- Dedup and sort timeline by timestamp when switching into a geohash\n- Keep content/layout unchanged; add lightweight debug logs for empty rows

- Use NSString.length for all NSRange regex scans
- Guard string slicing when lastEnd > match.lowerBound
- Advance lastEnd safely to avoid backtracking overlaps
- Apply to formatMessageContent, formatMessage, formatMessageAsText, parseMentions

bitchat/ViewModels/ChatViewModel.swift

@@ -382,6 +382,11 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
     @Published var showBluetoothAlert = false
     @Published var bluetoothAlertMessage = ""
     @Published var bluetoothState: CBManagerState = .unknown
+
+    // Presentation state for privacy gating
+    @Published var isLocationChannelsSheetPresented: Bool = false
+    @Published var isAppInfoPresented: Bool = false
+    @Published var showScreenshotPrivacyWarning: Bool = false
     
     // Messages are naturally ephemeral - no persistent storage
     // Persist mesh public timeline across channel switches
@@ -1407,6 +1412,11 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
         switch channel {
         case .mesh:
             messages = meshTimeline
+            // Debug: log if any empty messages are present
+            let emptyMesh = messages.filter { $0.content.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty }.count
+            if emptyMesh > 0 {
+                SecureLogger.log("RenderGuard: mesh timeline contains \(emptyMesh) empty messages", category: SecureLogger.session, level: .debug)
+            }
             stopGeoParticipantsTimer()
             geohashPeople = []
             teleportedGeo.removeAll()
@@ -1414,13 +1424,26 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
             // Sanitize existing timeline (filter any prior empty-content entries)
             var arr = geoTimelines[ch.geohash] ?? []
             arr.removeAll { $0.content.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty }
-            // Ensure chronological order when returning to a geohash
+            // Deduplicate by ID while preserving order (from oldest to newest)
             if arr.count > 1 {
-                arr.sort { $0.timestamp < $1.timestamp }
+                var seen = Set<String>()
+                var dedup: [BitchatMessage] = []
+                for m in arr.sorted(by: { $0.timestamp < $1.timestamp }) {
+                    if !seen.contains(m.id) {
+                        dedup.append(m)
+                        seen.insert(m.id)
+                    }
+                }
+                arr = dedup
             }
             // Persist the cleaned/sorted timeline for this geohash
             geoTimelines[ch.geohash] = arr
             messages = arr
+            // Debug: log if any empty messages are present post-sanitize
+            let emptyGeo = messages.filter { $0.content.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty }.count
+            if emptyGeo > 0 {
+                SecureLogger.log("RenderGuard: geohash \(ch.geohash) timeline has \(emptyGeo) empty messages after sanitize", category: SecureLogger.session, level: .debug)
+            }
         }
         // Unsubscribe previous
         if let sub = geoSubscriptionID {
@@ -2588,6 +2611,17 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
     
     @MainActor
     @objc private func userDidTakeScreenshot() {
+        // Respect privacy: do not broadcast screenshots taken from non-chat sheets
+        if isLocationChannelsSheetPresented {
+            // Show a warning about sharing location screenshots publicly
+            showScreenshotPrivacyWarning = true
+            return
+        }
+        if isAppInfoPresented {
+            // Silently ignore screenshots of app info
+            return
+        }
+
         // Send screenshot notification based on current context
         let screenshotMessage = "* \(nickname) took a screenshot *"
         
@@ -2607,7 +2641,7 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
                 }
             }
             
-            // Show local notification immediately as system message
+            // Show local notification immediately as system message (only in chat)
             let localNotification = BitchatMessage(
                 sender: "system",
                 content: "you took a screenshot",
@@ -2658,7 +2692,7 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
             }
             
 
-            // Show local notification immediately as system message
+            // Show local notification immediately as system message (only in chat)
             let localNotification = BitchatMessage(
                 sender: "system",
                 content: "you took a screenshot",
@@ -3043,8 +3077,10 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
         let mentionRegex = try? NSRegularExpression(pattern: mentionPattern, options: [])
         let hashtagRegex = try? NSRegularExpression(pattern: hashtagPattern, options: [])
         
-        let mentionMatches = mentionRegex?.matches(in: contentText, options: [], range: NSRange(location: 0, length: contentText.count)) ?? []
-        let hashtagMatches = hashtagRegex?.matches(in: contentText, options: [], range: NSRange(location: 0, length: contentText.count)) ?? []
+        let nsContent = contentText as NSString
+        let nsLen = nsContent.length
+        let mentionMatches = mentionRegex?.matches(in: contentText, options: [], range: NSRange(location: 0, length: nsLen)) ?? []
+        let hashtagMatches = hashtagRegex?.matches(in: contentText, options: [], range: NSRange(location: 0, length: nsLen)) ?? []
         
         // Combine and sort all matches
         var allMatches: [(range: NSRange, type: String)] = []
@@ -3061,12 +3097,14 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
         for (matchRange, matchType) in allMatches {
             // Add text before the match
             if let range = Range(matchRange, in: contentText) {
-                let beforeText = String(contentText[lastEndIndex..<range.lowerBound])
-                if !beforeText.isEmpty {
-                    var normalStyle = AttributeContainer()
-                    normalStyle.font = .system(size: 14, design: .monospaced)
-                    normalStyle.foregroundColor = isDark ? Color.white : Color.black
-                    processedContent.append(AttributedString(beforeText).mergingAttributes(normalStyle))
+                if lastEndIndex < range.lowerBound {
+                    let beforeText = String(contentText[lastEndIndex..<range.lowerBound])
+                    if !beforeText.isEmpty {
+                        var normalStyle = AttributeContainer()
+                        normalStyle.font = .system(size: 14, design: .monospaced)
+                        normalStyle.foregroundColor = isDark ? Color.white : Color.black
+                        processedContent.append(AttributedString(beforeText).mergingAttributes(normalStyle))
+                    }
                 }
                 
                 // Add the match with appropriate styling
@@ -3084,7 +3122,7 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
                 
                 processedContent.append(AttributedString(matchText).mergingAttributes(matchStyle))
                 
-                lastEndIndex = range.upperBound
+                if lastEndIndex < range.upperBound { lastEndIndex = range.upperBound }
             }
         }
         
@@ -3161,9 +3199,12 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
             
             // For extremely long content, render as plain text to avoid heavy regex/layout work,
             // unless the content includes Cashu tokens we want to chip-render below
+            // Compute NSString-backed length for regex/nsrange correctness with multi-byte characters
+            let nsContent = content as NSString
+            let nsLen = nsContent.length
             let containsCashuEarly: Bool = {
                 let rx = Regexes.quickCashuPresence
-                return rx.numberOfMatches(in: content, options: [], range: NSRange(location: 0, length: content.count)) > 0
+                return rx.numberOfMatches(in: content, options: [], range: NSRange(location: 0, length: nsLen)) > 0
             }()
             if (content.count > 4000 || content.hasVeryLongToken(threshold: 1024)) && !containsCashuEarly {
                 var plainStyle = AttributeContainer()
@@ -3181,8 +3222,6 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
             let lnurlRegex = Regexes.lnurl
             let lightningSchemeRegex = Regexes.lightningScheme
             let detector = Regexes.linkDetector
-            
-            let nsLen = content.count
             let hasMentionsHint = content.contains("@")
             let hasHashtagsHint = content.contains("#")
             let hasURLHint = content.contains("://") || content.contains("www.") || content.contains("http")
@@ -3262,17 +3301,19 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
             for (range, type) in allMatches {
                 // Add text before match
                 if let nsRange = Range(range, in: content) {
-                    let beforeText = String(content[lastEnd..<nsRange.lowerBound])
-                    if !beforeText.isEmpty {
-                        var beforeStyle = AttributeContainer()
-                        beforeStyle.foregroundColor = baseColor
-                        beforeStyle.font = isSelf
-                            ? .system(size: 14, weight: .bold, design: .monospaced)
-                            : .system(size: 14, design: .monospaced)
-                        if isMentioned {
-                            beforeStyle.font = beforeStyle.font?.bold()
+                    if lastEnd < nsRange.lowerBound {
+                        let beforeText = String(content[lastEnd..<nsRange.lowerBound])
+                        if !beforeText.isEmpty {
+                            var beforeStyle = AttributeContainer()
+                            beforeStyle.foregroundColor = baseColor
+                            beforeStyle.font = isSelf
+                                ? .system(size: 14, weight: .bold, design: .monospaced)
+                                : .system(size: 14, design: .monospaced)
+                            if isMentioned {
+                                beforeStyle.font = beforeStyle.font?.bold()
+                            }
+                            result.append(AttributedString(beforeText).mergingAttributes(beforeStyle))
                         }
-                        result.append(AttributedString(beforeText).mergingAttributes(beforeStyle))
                     }
                     
                     // Add styled match
@@ -3380,7 +3421,10 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
                             result.append(AttributedString(matchText).mergingAttributes(matchStyle))
                         }
                     }
-                    lastEnd = nsRange.upperBound
+                    // Advance lastEnd safely in case of overlaps
+                    if lastEnd < nsRange.upperBound {
+                        lastEnd = nsRange.upperBound
+                    }
                 }
             }
             
@@ -3478,19 +3522,23 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
             // Regular expression to find @mentions
             let pattern = "@([\\p{L}0-9_]+)"
             let regex = try? NSRegularExpression(pattern: pattern, options: [])
-            let matches = regex?.matches(in: contentText, options: [], range: NSRange(location: 0, length: contentText.count)) ?? []
+            let nsContent = contentText as NSString
+            let nsLen = nsContent.length
+            let matches = regex?.matches(in: contentText, options: [], range: NSRange(location: 0, length: nsLen)) ?? []
             
             var lastEndIndex = contentText.startIndex
             
             for match in matches {
                 // Add text before the mention
                 if let range = Range(match.range(at: 0), in: contentText) {
-                    let beforeText = String(contentText[lastEndIndex..<range.lowerBound])
-                    if !beforeText.isEmpty {
-                        var normalStyle = AttributeContainer()
-                        normalStyle.font = .system(size: 14, design: .monospaced)
-                        normalStyle.foregroundColor = isDark ? Color.white : Color.black
-                        processedContent.append(AttributedString(beforeText).mergingAttributes(normalStyle))
+                    if lastEndIndex < range.lowerBound {
+                        let beforeText = String(contentText[lastEndIndex..<range.lowerBound])
+                        if !beforeText.isEmpty {
+                            var normalStyle = AttributeContainer()
+                            normalStyle.font = .system(size: 14, design: .monospaced)
+                            normalStyle.foregroundColor = isDark ? Color.white : Color.black
+                            processedContent.append(AttributedString(beforeText).mergingAttributes(normalStyle))
+                        }
                     }
                     
                     // Add the mention with highlight
@@ -3500,7 +3548,7 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
                     mentionStyle.foregroundColor = Color.orange
                     processedContent.append(AttributedString(mentionText).mergingAttributes(mentionStyle))
                     
-                    lastEndIndex = range.upperBound
+                    if lastEndIndex < range.upperBound { lastEndIndex = range.upperBound }
                 }
             }
             
@@ -4698,7 +4746,9 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
         // Allow optional disambiguation suffix '#abcd' for duplicate nicknames
         let pattern = "@([\\p{L}0-9_]+(?:#[a-fA-F0-9]{4})?)"
         let regex = try? NSRegularExpression(pattern: pattern, options: [])
-        let matches = regex?.matches(in: content, options: [], range: NSRange(location: 0, length: content.count)) ?? []
+        let nsContent = content as NSString
+        let nsLen = nsContent.length
+        let matches = regex?.matches(in: content, options: [], range: NSRange(location: 0, length: nsLen)) ?? []
         
         var mentions: [String] = []
         let peerNicknames = meshService.getPeerNicknames()
@@ -5765,9 +5815,12 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
         if isGeo && finalMessage.sender != "system" {
             if let gh = currentGeohash {
                 var arr = geoTimelines[gh] ?? []
-                arr.append(finalMessage)
-                if arr.count > geoTimelineCap { arr = Array(arr.suffix(geoTimelineCap)) }
-                geoTimelines[gh] = arr
+                // Dedup by message ID before appending to per-geohash timeline
+                if !arr.contains(where: { $0.id == finalMessage.id }) {
+                    arr.append(finalMessage)
+                    if arr.count > geoTimelineCap { arr = Array(arr.suffix(geoTimelineCap)) }
+                    geoTimelines[gh] = arr
+                }
             }
         }
 

bitchat/Views/ContentView.swift

@@ -165,6 +165,8 @@ struct ContentView: View {
         }
         .sheet(isPresented: $showAppInfo) {
             AppInfoView()
+                .onAppear { viewModel.isAppInfoPresented = true }
+                .onDisappear { viewModel.isAppInfoPresented = false }
         }
         .sheet(isPresented: Binding(
             get: { viewModel.showingFingerprintFor != nil },
@@ -279,8 +281,10 @@ struct ContentView: View {
                         }
                     }()
                     let items = windowedMessages.map { (uiID: "\(contextKey)|\($0.id)", message: $0) }
-                    
-                    ForEach(items, id: \.uiID) { item in
+                    // Filter out empty/whitespace-only messages to avoid blank rows
+                    let filteredItems = items.filter { !$0.message.content.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty }
+
+                    ForEach(filteredItems, id: \.uiID) { item in
                         let message = item.message
                         VStack(alignment: .leading, spacing: 0) {
                             // Check if current user is mentioned
@@ -1182,6 +1186,13 @@ struct ContentView: View {
         .padding(.horizontal, 12)
         .sheet(isPresented: $showLocationChannelsSheet) {
             LocationChannelsSheet(isPresented: $showLocationChannelsSheet)
+                .onAppear { viewModel.isLocationChannelsSheetPresented = true }
+                .onDisappear { viewModel.isLocationChannelsSheetPresented = false }
+        }
+        .alert("heads up", isPresented: $viewModel.showScreenshotPrivacyWarning) {
+            Button("ok", role: .cancel) {}
+        } message: {
+            Text("screenshots of location channels will reveal your location. think before sharing publicly.")
         }
         .background(backgroundColor.opacity(0.95))
     }

bitchat/Views/LocationChannelsSheet.swift

@@ -304,22 +304,17 @@ struct LocationChannelsSheet: View {
                                 .foregroundColor(.secondary)
                         }
                     }
-                    HStack(spacing: 0) {
-                        Text(subtitlePrefix)
-                            .font(.system(size: 12, design: .monospaced))
-                            .foregroundColor(.secondary)
-                        if let name = subtitleName {
-                            Text(" • ")
-                                .font(.system(size: 12, design: .monospaced))
-                                .foregroundColor(.secondary)
-                            Text(name)
-                                .font(.system(size: 12, design: .monospaced))
-                                .fontWeight(subtitleNameBold ? .bold : .regular)
-                                .foregroundColor(.secondary)
-                                .lineLimit(1)
-                                .truncationMode(.tail)
-                        }
+                let subtitleFull: String = {
+                    if let name = subtitleName, !name.isEmpty {
+                        return subtitlePrefix + " • " + name
                     }
+                    return subtitlePrefix
+                }()
+                Text(subtitleFull)
+                    .font(.system(size: 12, design: .monospaced))
+                    .foregroundColor(.secondary)
+                    .lineLimit(1)
+                    .truncationMode(.tail)
                 }
                 Spacer()
                 if isSelected {