diff --git a/bitchat/Services/GeohashParticipantTracker.swift b/bitchat/Services/GeohashParticipantTracker.swift
new file mode 100644
index 00000000..1bd2df02
--- /dev/null
+++ b/bitchat/Services/GeohashParticipantTracker.swift
@@ -0,0 +1,159 @@
+//
+// GeohashParticipantTracker.swift
+// bitchat
+//
+// Tracks participants in geohash-based location channels.
+// This is free and unencumbered software released into the public domain.
+//
+
+import Foundation
+
+/// Represents a participant in a geohash channel
+public struct GeoPerson: Identifiable, Equatable, Sendable {
+    public let id: String        // pubkey hex (lowercased)
+    public let displayName: String
+    public let lastSeen: Date
+
+    public init(id: String, displayName: String, lastSeen: Date) {
+        self.id = id
+        self.displayName = displayName
+        self.lastSeen = lastSeen
+    }
+}
+
+/// Protocol for resolving display names and checking block status
+@MainActor
+public protocol GeohashParticipantContext: AnyObject {
+    /// Returns display name for a Nostr pubkey (e.g., "alice#a1b2" or "anon#c3d4")
+    func displayNameForPubkey(_ pubkeyHex: String) -> String
+    /// Returns true if the pubkey is blocked
+    func isBlocked(_ pubkeyHexLowercased: String) -> Bool
+}
+
+/// Tracks participants across multiple geohash channels
+@MainActor
+public final class GeohashParticipantTracker: ObservableObject {
+
+    /// Activity cutoff duration (defaults to 5 minutes)
+    public let activityCutoff: TimeInterval
+
+    /// Per-geohash participant map: [geohash: [pubkeyHex: lastSeen]]
+    private var participants: [String: [String: Date]] = [:]
+
+    /// Currently visible people for the active geohash
+    @Published public private(set) var visiblePeople: [GeoPerson] = []
+
+    /// The currently active geohash (if any)
+    private var activeGeohash: String?
+
+    /// Context for display name resolution and block checking
+    private weak var context: GeohashParticipantContext?
+
+    /// Timer for periodic refresh
+    private var refreshTimer: Timer?
+
+    public init(activityCutoff: TimeInterval = -300) { // default 5 minutes
+        self.activityCutoff = activityCutoff
+    }
+
+    /// Configure with a context provider
+    public func configure(context: GeohashParticipantContext) {
+        self.context = context
+    }
+
+    /// Set the currently active geohash
+    public func setActiveGeohash(_ geohash: String?) {
+        activeGeohash = geohash
+        if geohash == nil {
+            visiblePeople = []
+        } else {
+            refresh()
+        }
+    }
+
+    /// Record activity from a participant in the current active geohash
+    public func recordParticipant(pubkeyHex: String) {
+        guard let gh = activeGeohash else { return }
+        recordParticipant(pubkeyHex: pubkeyHex, geohash: gh)
+    }
+
+    /// Record activity from a participant in a specific geohash
+    public func recordParticipant(pubkeyHex: String, geohash: String) {
+        let key = pubkeyHex.lowercased()
+        var map = participants[geohash] ?? [:]
+        map[key] = Date()
+        participants[geohash] = map
+
+        // Only refresh visible list if this geohash is currently active
+        if activeGeohash == geohash {
+            refresh()
+        }
+    }
+
+    /// Remove a participant from all geohashes (used when blocking)
+    public func removeParticipant(pubkeyHex: String) {
+        let key = pubkeyHex.lowercased()
+        for (gh, var map) in participants {
+            map.removeValue(forKey: key)
+            participants[gh] = map
+        }
+        refresh()
+    }
+
+    /// Get participant count for a specific geohash
+    public func participantCount(for geohash: String) -> Int {
+        let cutoff = Date().addingTimeInterval(activityCutoff)
+        let map = participants[geohash] ?? [:]
+        return map.values.filter { $0 >= cutoff }.count
+    }
+
+    /// Get the visible people list for the active geohash (read-only query)
+    public func getVisiblePeople() -> [GeoPerson] {
+        guard let gh = activeGeohash, let context = context else { return [] }
+        let cutoff = Date().addingTimeInterval(activityCutoff)
+        let map = (participants[gh] ?? [:])
+            .filter { $0.value >= cutoff }
+            .filter { !context.isBlocked($0.key) }
+
+        return map
+            .map { (pub, seen) in
+                GeoPerson(id: pub, displayName: context.displayNameForPubkey(pub), lastSeen: seen)
+            }
+            .sorted { $0.lastSeen > $1.lastSeen }
+    }
+
+    /// Refresh the visible people list
+    public func refresh() {
+        visiblePeople = getVisiblePeople()
+    }
+
+    /// Start the periodic refresh timer
+    public func startRefreshTimer(interval: TimeInterval = 30.0) {
+        stopRefreshTimer()
+        refreshTimer = Timer.scheduledTimer(withTimeInterval: interval, repeats: true) { [weak self] _ in
+            Task { @MainActor in
+                self?.refresh()
+            }
+        }
+    }
+
+    /// Stop the periodic refresh timer
+    public func stopRefreshTimer() {
+        refreshTimer?.invalidate()
+        refreshTimer = nil
+    }
+
+    /// Clear all participant data
+    public func clear() {
+        participants.removeAll()
+        visiblePeople = []
+    }
+
+    /// Clear participant data for a specific geohash
+    public func clear(geohash: String) {
+        participants.removeValue(forKey: geohash)
+        if activeGeohash == geohash {
+            visiblePeople = []
+        }
+    }
+}
diff --git a/bitchat/Services/MessageFormattingEngine.swift b/bitchat/Services/MessageFormattingEngine.swift
new file mode 100644
index 00000000..934c3f41
--- /dev/null
+++ b/bitchat/Services/MessageFormattingEngine.swift
@@ -0,0 +1,471 @@
+//
+// MessageFormattingEngine.swift
+// bitchat
+//
+// Handles message text formatting, including mentions, hashtags, URLs, and tokens.
+// This is free and unencumbered software released into the public domain.
+//
+
+import Foundation
+import SwiftUI
+
+// MARK: - Formatting Context Protocol
+
+/// Protocol defining the context needed for message formatting.
+/// Implemented by ChatViewModel to provide runtime state.
+@MainActor
+protocol MessageFormattingContext: AnyObject {
+    /// The user's current nickname
+    var nickname: String { get }
+
+    /// Determines if a message was sent by the current user
+    func isSelfMessage(_ message: BitchatMessage) -> Bool
+
+    /// Gets the color for a message's sender
+    func senderColor(for message: BitchatMessage, isDark: Bool) -> Color
+
+    /// Resolves a peer ID to a clickable URL
+    func peerURL(for peerID: PeerID) -> URL?
+}
+
+// MARK: - Formatting Engine
+
+/// Handles rich text formatting for chat messages.
+/// Extracts mentions, hashtags, URLs, Lightning invoices, and Cashu tokens.
+final class MessageFormattingEngine {
+
+    // MARK: - Precompiled Regexes
+
+    /// Precompiled regex patterns for message content parsing
+    enum Patterns {
+        static let hashtag: NSRegularExpression = {
+            try! NSRegularExpression(pattern: "#([a-zA-Z0-9_]+)", options: [])
+        }()
+
+        static let mention: NSRegularExpression = {
+            try! NSRegularExpression(pattern: "@([\\p{L}0-9_]+(?:#[a-fA-F0-9]{4})?)", options: [])
+        }()
+
+        static let cashu: NSRegularExpression = {
+            try! NSRegularExpression(pattern: "\\bcashu[AB][A-Za-z0-9._-]{40,}\\b", options: [])
+        }()
+
+        static let bolt11: NSRegularExpression = {
+            try! NSRegularExpression(pattern: "(?i)\\bln(bc|tb|bcrt)[0-9][a-z0-9]{50,}\\b", options: [])
+        }()
+
+        static let lnurl: NSRegularExpression = {
+            try! NSRegularExpression(pattern: "(?i)\\blnurl1[a-z0-9]{20,}\\b", options: [])
+        }()
+
+        static let lightningScheme: NSRegularExpression = {
+            try! NSRegularExpression(pattern: "(?i)\\blightning:[^\\s]+", options: [])
+        }()
+
+        static let linkDetector: NSDataDetector? = {
+            try? NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue)
+        }()
+
+        static let quickCashuPresence: NSRegularExpression = {
+            try! NSRegularExpression(pattern: "\\bcashu[AB][A-Za-z0-9._-]{40,}\\b", options: [])
+        }()
+
+        static let simplifyHTTPURL: NSRegularExpression = {
+            try! NSRegularExpression(pattern: "https?://[^\\s?#]+(?:[?#][^\\s]*)?", options: [.caseInsensitive])
+        }()
+    }
+
+    // MARK: - Match Types
+
+    /// Types of matches found in message content
+    enum MatchType: String {
+        case hashtag
+        case mention
+        case url
+        case cashu
+        case lightning
+        case bolt11
+        case lnurl
+    }
+
+    /// A match found in message content
+    struct ContentMatch {
+        let range: NSRange
+        let type: MatchType
+    }
+
+    // MARK: - Public API
+
+    /// Formats a message with rich text styling
+    @MainActor
+    static func formatMessage(
+        _ message: BitchatMessage,
+        context: MessageFormattingContext,
+        colorScheme: ColorScheme
+    ) -> AttributedString {
+        let isDark = colorScheme == .dark
+        let isSelf = context.isSelfMessage(message)
+
+        // Check cache first
+        if let cached = message.getCachedFormattedText(isDark: isDark, isSelf: isSelf) {
+            return cached
+        }
+
+        var result = AttributedString()
+        let baseColor: Color = isSelf ? .orange : context.senderColor(for: message, isDark: isDark)
+
+        // Format system messages differently
+        if message.sender == "system" {
+            result = formatSystemMessage(message, isDark: isDark)
+        } else {
+            // Format sender header
+            result = formatSenderHeader(
+                message: message,
+                baseColor: baseColor,
+                isSelf: isSelf,
+                context: context
+            )
+
+            // Format content
+            let contentResult = formatContent(
+                message.content,
+                baseColor: baseColor,
+                isSelf: isSelf,
+                isMentioned: message.mentions?.contains(context.nickname) ?? false
+            )
+            result.append(contentResult)
+
+            // Add timestamp
+            result.append(formatTimestamp(message.formattedTimestamp))
+        }
+
+        // Cache the result
+        message.setCachedFormattedText(result, isDark: isDark, isSelf: isSelf)
+
+        return result
+    }
+
+    /// Formats just the message header (sender portion)
+    @MainActor
+    static func formatHeader(
+        _ message: BitchatMessage,
+        context: MessageFormattingContext,
+        colorScheme: ColorScheme
+    ) -> AttributedString {
+        let isDark = colorScheme == .dark
+        let isSelf = context.isSelfMessage(message)
+        let baseColor: Color = isSelf ? .orange : context.senderColor(for: message, isDark: isDark)
+
+        if message.sender == "system" {
+            var style = AttributeContainer()
+            style.foregroundColor = baseColor
+            style.font = .bitchatSystem(size: 14, weight: .medium, design: .monospaced)
+            return AttributedString(message.sender).mergingAttributes(style)
+        }
+
+        return formatSenderHeader(
+            message: message,
+            baseColor: baseColor,
+            isSelf: isSelf,
+            context: context
+        )
+    }
+
+    /// Extracts mentions from message content
+    static func extractMentions(from content: String) -> [String] {
+        let nsContent = content as NSString
+        let range = NSRange(location: 0, length: nsContent.length)
+        let matches = Patterns.mention.matches(in: content, options: [], range: range)
+
+        return matches.compactMap { match -> String? in
+            guard match.numberOfRanges > 1 else { return nil }
+            let captureRange = match.range(at: 1)
+            guard let swiftRange = Range(captureRange, in: content) else { return nil }
+            return String(content[swiftRange])
+        }
+    }
+
+    /// Checks if content contains a Cashu token
+    static func containsCashuToken(_ content: String) -> Bool {
+        let nsContent = content as NSString
+        let range = NSRange(location: 0, length: nsContent.length)
+        return Patterns.quickCashuPresence.numberOfMatches(in: content, options: [], range: range) > 0
+    }
+
+    // MARK: - Private Helpers
+
+    private static func formatSystemMessage(_ message: BitchatMessage, isDark: Bool) -> AttributedString {
+        var result = AttributedString()
+
+        let content = AttributedString("* \(message.content) *")
+        var contentStyle = AttributeContainer()
+        contentStyle.foregroundColor = Color.gray
+        contentStyle.font = .bitchatSystem(size: 12, design: .monospaced).italic()
+        result.append(content.mergingAttributes(contentStyle))
+
+        // Add timestamp
+        let timestamp = AttributedString(" [\(message.formattedTimestamp)]")
+        var timestampStyle = AttributeContainer()
+        timestampStyle.foregroundColor = Color.gray.opacity(0.5)
+        timestampStyle.font = .bitchatSystem(size: 10, design: .monospaced)
+        result.append(timestamp.mergingAttributes(timestampStyle))
+
+        return result
+    }
+
+    @MainActor
+    private static func formatSenderHeader(
+        message: BitchatMessage,
+        baseColor: Color,
+        isSelf: Bool,
+        context: MessageFormattingContext
+    ) -> AttributedString {
+        var result = AttributedString()
+
+        let (baseName, suffix) = message.sender.splitSuffix()
+        var senderStyle = AttributeContainer()
+        senderStyle.foregroundColor = baseColor
+        let fontWeight: Font.Weight = isSelf ? .bold : .medium
+        senderStyle.font = .bitchatSystem(size: 14, weight: fontWeight, design: .monospaced)
+
+        // Make sender clickable
+        if let spid = message.senderPeerID, let url = context.peerURL(for: spid) {
+            senderStyle.link = url
+        }
+
+        // Build: "<@baseName#suffix> "
+        result.append(AttributedString("<@").mergingAttributes(senderStyle))
+        result.append(AttributedString(baseName).mergingAttributes(senderStyle))
+
+        if !suffix.isEmpty {
+            var suffixStyle = senderStyle
+            suffixStyle.foregroundColor = baseColor.opacity(0.6)
+            result.append(AttributedString(suffix).mergingAttributes(suffixStyle))
+        }
+
+        result.append(AttributedString("> ").mergingAttributes(senderStyle))
+
+        return result
+    }
+
+    private static func formatContent(
+        _ content: String,
+        baseColor: Color,
+        isSelf: Bool,
+        isMentioned: Bool
+    ) -> AttributedString {
+        // For very long content without special tokens, use plain formatting
+        let containsCashu = containsCashuToken(content)
+        if (content.count > 4000 || content.hasVeryLongToken(threshold: 1024)) && !containsCashu {
+            return formatPlainContent(content, baseColor: baseColor, isSelf: isSelf)
+        }
+
+        // Find all matches
+        let matches = findAllMatches(in: content)
+
+        // Build formatted content
+        var result = AttributedString()
+        var lastEnd = content.startIndex
+
+        for match in matches {
+            guard let swiftRange = Range(match.range, in: content) else { continue }
+
+            // Add text before match
+            if lastEnd < swiftRange.lowerBound {
+                let beforeText = String(content[lastEnd..<swiftRange.lowerBound])
+                result.append(formatPlainText(beforeText, baseColor: baseColor, isSelf: isSelf, isMentioned: isMentioned))
+            }
+
+            // Add styled match
+            let matchText = String(content[swiftRange])
+            result.append(formatMatch(matchText, type: match.type, baseColor: baseColor, isSelf: isSelf))
+
+            lastEnd = swiftRange.upperBound
+        }
+
+        // Add remaining text
+        if lastEnd < content.endIndex {
+            let remainingText = String(content[lastEnd...])
+            result.append(formatPlainText(remainingText, baseColor: baseColor, isSelf: isSelf, isMentioned: isMentioned))
+        }
+
+        return result
+    }
+
+    private static func findAllMatches(in content: String) -> [ContentMatch] {
+        let nsContent = content as NSString
+        let nsLen = nsContent.length
+        let fullRange = NSRange(location: 0, length: nsLen)
+
+        // Quick hints to avoid unnecessary regex work
+        let hasMentions = content.contains("@")
+        let hasHashtags = content.contains("#")
+        let hasURLs = content.contains("://") || content.contains("www.") || content.contains("http")
+        let hasLightning = content.lowercased().contains("ln") || content.lowercased().contains("lightning:")
+        let hasCashu = content.lowercased().contains("cashu")
+
+        // Collect matches
+        let mentionMatches = hasMentions ? Patterns.mention.matches(in: content, options: [], range: fullRange) : []
+        let hashtagMatches = hasHashtags ? Patterns.hashtag.matches(in: content, options: [], range: fullRange) : []
+        let urlMatches = hasURLs ? (Patterns.linkDetector?.matches(in: content, options: [], range: fullRange) ?? []) : []
+        let cashuMatches = hasCashu ? Patterns.cashu.matches(in: content, options: [], range: fullRange) : []
+        let lightningMatches = hasLightning ? Patterns.lightningScheme.matches(in: content, options: [], range: fullRange) : []
+        let bolt11Matches = hasLightning ? Patterns.bolt11.matches(in: content, options: [], range: fullRange) : []
+        let lnurlMatches = hasLightning ? Patterns.lnurl.matches(in: content, options: [], range: fullRange) : []
+
+        // Build mention ranges for overlap checking
+        let mentionRanges = mentionMatches.map { $0.range(at: 0) }
+
+        func overlapsMention(_ r: NSRange) -> Bool {
+            mentionRanges.contains { NSIntersectionRange(r, $0).length > 0 }
+        }
+
+        func isStandaloneHashtag(_ r: NSRange) -> Bool {
+            guard let swiftRange = Range(r, in: content) else { return false }
+            if swiftRange.lowerBound == content.startIndex { return true }
+            let prev = content.index(before: swiftRange.lowerBound)
+            return content[prev].isWhitespace || content[prev].isNewline
+        }
+
+        func attachedToMention(_ r: NSRange) -> Bool {
+            guard let swiftRange = Range(r, in: content), swiftRange.lowerBound > content.startIndex else { return false }
+            var i = content.index(before: swiftRange.lowerBound)
+            while true {
+                let ch = content[i]
+                if ch.isWhitespace || ch.isNewline { break }
+                if ch == "@" { return true }
+                if i == content.startIndex { break }
+                i = content.index(before: i)
+            }
+            return false
+        }
+
+        var allMatches: [ContentMatch] = []
+
+        // Add hashtags (excluding those attached to mentions)
+        for match in hashtagMatches {
+            let range = match.range(at: 0)
+            if !overlapsMention(range) && !attachedToMention(range) && isStandaloneHashtag(range) {
+                allMatches.append(ContentMatch(range: range, type: .hashtag))
+            }
+        }
+
+        // Add mentions
+        for match in mentionMatches {
+            allMatches.append(ContentMatch(range: match.range(at: 0), type: .mention))
+        }
+
+        // Add URLs
+        for match in urlMatches where !overlapsMention(match.range) {
+            allMatches.append(ContentMatch(range: match.range, type: .url))
+        }
+
+        // Add Cashu tokens
+        for match in cashuMatches where !overlapsMention(match.range(at: 0)) {
+            allMatches.append(ContentMatch(range: match.range(at: 0), type: .cashu))
+        }
+
+        // Add Lightning scheme URLs
+        for match in lightningMatches where !overlapsMention(match.range(at: 0)) {
+            allMatches.append(ContentMatch(range: match.range(at: 0), type: .lightning))
+        }
+
+        // Add bolt11/lnurl (avoiding overlaps with lightning scheme and URLs)
+        let occupied = urlMatches.map { $0.range } + lightningMatches.map { $0.range(at: 0) }
+        func overlapsOccupied(_ r: NSRange) -> Bool {
+            occupied.contains { NSIntersectionRange(r, $0).length > 0 }
+        }
+
+        for match in bolt11Matches where !overlapsMention(match.range(at: 0)) && !overlapsOccupied(match.range(at: 0)) {
+            allMatches.append(ContentMatch(range: match.range(at: 0), type: .bolt11))
+        }
+
+        for match in lnurlMatches where !overlapsMention(match.range(at: 0)) && !overlapsOccupied(match.range(at: 0)) {
+            allMatches.append(ContentMatch(range: match.range(at: 0), type: .lnurl))
+        }
+
+        // Sort by position
+        return allMatches.sorted { $0.range.location < $1.range.location }
+    }
+
+    private static func formatPlainContent(_ content: String, baseColor: Color, isSelf: Bool) -> AttributedString {
+        var style = AttributeContainer()
+        style.foregroundColor = baseColor
+        style.font = isSelf
+            ? .bitchatSystem(size: 14, weight: .bold, design: .monospaced)
+            : .bitchatSystem(size: 14, design: .monospaced)
+        return AttributedString(content).mergingAttributes(style)
+    }
+
+    private static func formatPlainText(_ text: String, baseColor: Color, isSelf: Bool, isMentioned: Bool) -> AttributedString {
+        guard !text.isEmpty else { return AttributedString() }
+
+        var style = AttributeContainer()
+        style.foregroundColor = baseColor
+        style.font = isSelf
+            ? .bitchatSystem(size: 14, weight: .bold, design: .monospaced)
+            : .bitchatSystem(size: 14, design: .monospaced)
+
+        if isMentioned {
+            style.font = style.font?.bold()
+        }
+
+        return AttributedString(text).mergingAttributes(style)
+    }
+
+    private static func formatMatch(_ text: String, type: MatchType, baseColor: Color, isSelf: Bool) -> AttributedString {
+        var style = AttributeContainer()
+
+        switch type {
+        case .mention:
+            // Split optional '#abcd' suffix
+            let (baseName, suffix) = text.splitSuffix()
+            var result = AttributedString()
+
+            var mentionStyle = AttributeContainer()
+            mentionStyle.foregroundColor = .blue
+            mentionStyle.font = .bitchatSystem(size: 14, weight: .semibold, design: .monospaced)
+            result.append(AttributedString(baseName).mergingAttributes(mentionStyle))
+
+            if !suffix.isEmpty {
+                var suffixStyle = mentionStyle
+                suffixStyle.foregroundColor = Color.gray.opacity(0.7)
+                result.append(AttributedString(suffix).mergingAttributes(suffixStyle))
+            }
+
+            return result
+
+        case .hashtag:
+            style.foregroundColor = .purple
+            style.font = .bitchatSystem(size: 14, weight: .medium, design: .monospaced)
+
+        case .url:
+            style.foregroundColor = .blue
+            style.font = .bitchatSystem(size: 14, design: .monospaced)
+            style.underlineStyle = .single
+            if let url = URL(string: text) {
+                style.link = url
+            }
+
+        case .cashu:
+            style.foregroundColor = .green
+            style.font = .bitchatSystem(size: 14, weight: .medium, design: .monospaced)
+            style.backgroundColor = Color.green.opacity(0.1)
+
+        case .lightning, .bolt11, .lnurl:
+            style.foregroundColor = .yellow
+            style.font = .bitchatSystem(size: 14, weight: .medium, design: .monospaced)
+            style.backgroundColor = Color.yellow.opacity(0.1)
+        }
+
+        return AttributedString(text).mergingAttributes(style)
+    }
+
+    private static func formatTimestamp(_ timestamp: String) -> AttributedString {
+        let text = AttributedString(" [\(timestamp)]")
+        var style = AttributeContainer()
+        style.foregroundColor = Color.gray.opacity(0.5)
+        style.font = .bitchatSystem(size: 10, design: .monospaced)
+        return text.mergingAttributes(style)
+    }
+}
diff --git a/bitchat/ViewModels/ChatViewModel.swift b/bitchat/ViewModels/ChatViewModel.swift
index cea5e752..0e7bcd61 100644
--- a/bitchat/ViewModels/ChatViewModel.swift
+++ b/bitchat/ViewModels/ChatViewModel.swift
@@ -92,7 +92,7 @@ import UniformTypeIdentifiers
 /// Manages the application state and business logic for BitChat.
 /// Acts as the primary coordinator between UI components and backend services,
 /// implementing the BitchatDelegate protocol to handle network events.
-final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProvider {
+final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProvider, GeohashParticipantContext, MessageFormattingContext {
     // Precompiled regexes and detectors reused across formatting
     private enum Regexes {
         static let hashtag: NSRegularExpression = {
@@ -419,10 +419,8 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
     private var lastPublicActivityAt: [String: Date] = [:]   // channelKey -> last activity time
     private var lastPublicActivityNotifyAt: [String: Date] = [:]
     private let channelInactivityThreshold: TimeInterval = TransportConfig.uiChannelInactivityThresholdSeconds
-    // Geohash participants (per geohash: pubkey -> lastSeen)
-    private var geoParticipants: [String: [String: Date]] = [:]
-    @Published private(set) var geohashPeople: [GeoPerson] = []
-    private var geoParticipantsTimer: Timer? = nil
+    // Geohash participant tracker
+    let participantTracker = GeohashParticipantTracker(activityCutoff: -TransportConfig.uiRecentCutoffFiveMinutesSeconds)
     // Participants who indicated they teleported (by tag in their events)
     @Published private(set) var teleportedGeo: Set<String> = []  // lowercased pubkey hex
     // Sampling subscriptions for multiple geohashes (when channel sheet is open)
@@ -526,6 +524,7 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
         
         // Wire up dependencies
         self.commandProcessor.chatViewModel = self
+        self.participantTracker.configure(context: self)
         
         // Subscribe to privateChatManager changes to trigger UI updates
         privateChatManager.objectWillChange
@@ -533,6 +532,13 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
                 self?.objectWillChange.send()
             }
             .store(in: &cancellables)
+
+        // Subscribe to participantTracker changes to trigger UI updates
+        participantTracker.objectWillChange
+            .sink { [weak self] _ in
+                self?.objectWillChange.send()
+            }
+            .store(in: &cancellables)
         self.commandProcessor.meshService = meshService
         
         loadNickname()
@@ -873,7 +879,7 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
             return
         }
         // Ensure participant decay timer is running
-        startGeoParticipantsTimer()
+        participantTracker.startRefreshTimer()
         // Unsubscribe + resubscribe
         NostrRelayManager.shared.unsubscribe(id: subID)
         let filter = NostrFilter.geohashEphemeral(
@@ -932,7 +938,7 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
         nostrKeyMapping[PeerID(nostr: event.pubkey)] = event.pubkey
 
         // Update participants last-seen for this pubkey
-        recordGeoParticipant(pubkeyHex: event.pubkey)
+        participantTracker.recordParticipant(pubkeyHex: event.pubkey)
         
         // Track teleported tag (only our format ["t","teleport"]) for icon state
         let hasTeleportTag = event.tags.contains(where: { tag in
@@ -1479,7 +1485,7 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
         }
 
         // Track ourselves as active participant
-        recordGeoParticipant(pubkeyHex: identity.publicKeyHex)
+        participantTracker.recordParticipant(pubkeyHex: identity.publicKeyHex)
         nostrKeyMapping[PeerID(nostr: identity.publicKeyHex)] = identity.publicKeyHex
         SecureLogger.debug("GeoTeleport: sent geo message pub=\(identity.publicKeyHex.prefix(8))… teleported=\(context.teleported)", category: .session)
 
@@ -1514,8 +1520,8 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
             if emptyMesh > 0 {
                 SecureLogger.debug("RenderGuard: mesh timeline contains \(emptyMesh) empty messages", category: .session)
             }
-            stopGeoParticipantsTimer()
-            geohashPeople = []
+            participantTracker.stopRefreshTimer()
+            participantTracker.setActiveGeohash(nil)
             teleportedGeo.removeAll()
         case .location:
             refreshVisibleMessages(from: channel)
@@ -1536,16 +1542,17 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
             geoDmSubscriptionID = nil
         }
         currentGeohash = nil
+        participantTracker.setActiveGeohash(nil)
         // Reset nickname cache for geochat participants
         geoNicknames.removeAll()
-        geohashPeople = []
-        
+
         guard case .location(let ch) = channel else { return }
         currentGeohash = ch.geohash
+        participantTracker.setActiveGeohash(ch.geohash)
         
         // Ensure self appears immediately in the people list; mark teleported state only when truly teleported
         if let id = try? idBridge.deriveIdentity(forGeohash: ch.geohash) {
-            recordGeoParticipant(pubkeyHex: id.publicKeyHex)
+            participantTracker.recordParticipant(pubkeyHex: id.publicKeyHex)
             let hasRegional = !LocationChannelManager.shared.availableChannels.isEmpty
             let inRegional = LocationChannelManager.shared.availableChannels.contains { $0.geohash == ch.geohash }
             let key = id.publicKeyHex.lowercased()
@@ -1559,7 +1566,7 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
         
         let subID = "geo-\(ch.geohash)"
         geoSubscriptionID = subID
-        startGeoParticipantsTimer()
+        participantTracker.startRefreshTimer()
         let ts = Date().addingTimeInterval(-TransportConfig.nostrGeohashInitialLookbackSeconds)
         let filter = NostrFilter.geohashEphemeral(ch.geohash, since: ts, limit: TransportConfig.nostrGeohashInitialLimit)
         let subRelays = GeoRelayDirectory.shared.closestRelays(toGeohash: ch.geohash, count: 5)
@@ -1629,7 +1636,7 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
         nostrKeyMapping[PeerID(nostr: event.pubkey)] = event.pubkey
         
         // Update participants last-seen for this pubkey
-        recordGeoParticipant(pubkeyHex: event.pubkey)
+        participantTracker.recordParticipant(pubkeyHex: event.pubkey)
         
         let senderName = displayNameForNostrPubkey(event.pubkey)
         let content = event.content
@@ -1811,49 +1818,6 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
     }
 
     // MARK: - Geohash Participants
-    struct GeoPerson: Identifiable, Equatable {
-        let id: String        // pubkey hex (lowercased)
-        let displayName: String
-        let lastSeen: Date
-    }
-
-    private func recordGeoParticipant(pubkeyHex: String) {
-        guard let gh = currentGeohash else { return }
-        let key = pubkeyHex.lowercased()
-        var map = geoParticipants[gh] ?? [:]
-        map[key] = Date()
-        geoParticipants[gh] = map
-        refreshGeohashPeople()
-    }
-
-    private func recordGeoParticipant(pubkeyHex: String, geohash: String) {
-        let key = pubkeyHex.lowercased()
-        var map = geoParticipants[geohash] ?? [:]
-        map[key] = Date()
-        geoParticipants[geohash] = map
-        // Only refresh list if this geohash is currently selected
-        if currentGeohash == geohash {
-            refreshGeohashPeople()
-        }
-    }
-
-    private func refreshGeohashPeople() {
-        guard let gh = currentGeohash else { geohashPeople = []; return }
-        let cutoff = Date().addingTimeInterval(-TransportConfig.uiRecentCutoffFiveMinutesSeconds)
-        var map = geoParticipants[gh] ?? [:]
-        // Prune expired entries
-        map = map.filter { $0.value >= cutoff }
-        // Remove blocked Nostr pubkeys
-        map = map.filter { !identityManager.isNostrBlocked(pubkeyHexLowercased: $0.key) }
-        geoParticipants[gh] = map
-        // Build display list
-        let people = map
-            .map { (pub, seen) in
-                GeoPerson(id: pub, displayName: displayNameForNostrPubkey(pub), lastSeen: seen)
-            }
-            .sorted { $0.lastSeen > $1.lastSeen }
-        geohashPeople = people
-    }
 
     @MainActor
     func isSelfSender(peerID: PeerID?, displayName: String?) -> Bool {
@@ -1878,33 +1842,17 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
         return false
     }
 
-    private func startGeoParticipantsTimer() {
-        stopGeoParticipantsTimer()
-        geoParticipantsTimer = Timer.scheduledTimer(withTimeInterval: 30.0, repeats: true) { [weak self] _ in
-            Task { @MainActor in
-                self?.refreshGeohashPeople()
-            }
-        }
+    // MARK: - Public helpers
+
+    /// Published geohash people list for SwiftUI observation
+    var geohashPeople: [GeoPerson] {
+        participantTracker.visiblePeople
     }
 
-    private func stopGeoParticipantsTimer() {
-        geoParticipantsTimer?.invalidate()
-        geoParticipantsTimer = nil
-    }
-    
-    // MARK: - Public helpers
     /// Return the current, pruned, sorted people list for the active geohash without mutating state.
     @MainActor
     func visibleGeohashPeople() -> [GeoPerson] {
-        guard let gh = currentGeohash else { return [] }
-        let cutoff = Date().addingTimeInterval(-TransportConfig.uiRecentCutoffFiveMinutesSeconds)
-        let map = (geoParticipants[gh] ?? [:])
-            .filter { $0.value >= cutoff }
-            .filter { !identityManager.isNostrBlocked(pubkeyHexLowercased: $0.key) }
-        let people = map
-            .map { (pub, seen) in GeoPerson(id: pub, displayName: displayNameForNostrPubkey(pub), lastSeen: seen) }
-            .sorted { $0.lastSeen > $1.lastSeen }
-        return people
+        participantTracker.getVisiblePeople()
     }
 
     /// CommandContextProvider conformance - returns visible geo participants
@@ -1914,9 +1862,17 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
     /// Returns the current participant count for a specific geohash, using the 5-minute activity window.
     @MainActor
     func geohashParticipantCount(for geohash: String) -> Int {
-        let cutoff = Date().addingTimeInterval(-TransportConfig.uiRecentCutoffFiveMinutesSeconds)
-        let map = geoParticipants[geohash] ?? [:]
-        return map.values.filter { $0 >= cutoff }.count
+        participantTracker.participantCount(for: geohash)
+    }
+
+    // MARK: - GeohashParticipantContext Protocol
+
+    func displayNameForPubkey(_ pubkeyHex: String) -> String {
+        displayNameForNostrPubkey(pubkeyHex)
+    }
+
+    func isBlocked(_ pubkeyHexLowercased: String) -> Bool {
+        identityManager.isNostrBlocked(pubkeyHexLowercased: pubkeyHexLowercased)
     }
 
     // Geohash block helpers
@@ -1928,13 +1884,9 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
     func blockGeohashUser(pubkeyHexLowercased: String, displayName: String) {
         let hex = pubkeyHexLowercased.lowercased()
         identityManager.setNostrBlocked(hex, isBlocked: true)
-        
+
         // Remove from participants for all geohashes
-        for (gh, var map) in geoParticipants {
-            map.removeValue(forKey: hex)
-            geoParticipants[gh] = map
-        }
-        refreshGeohashPeople()
+        participantTracker.removeParticipant(pubkeyHex: hex)
         
         // Remove their public messages from current geohash timeline and visible list
         if let gh = currentGeohash {
@@ -2022,13 +1974,12 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
     
     private func subscribeNostrEvent(_ event: NostrEvent, gh: String) {
         guard event.kind == NostrProtocol.EventKind.ephemeralEvent.rawValue else { return }
-        
+
         // Compute current participant count (5-minute window) BEFORE updating with this event
-        let cutoff = Date().addingTimeInterval(-TransportConfig.uiRecentCutoffFiveMinutesSeconds)
-        let existingCount = geoParticipants[gh]?.values.filter { $0 >= cutoff }.count ?? 0
-        
+        let existingCount = participantTracker.participantCount(for: gh)
+
         // Update participants for this specific geohash
-        recordGeoParticipant(pubkeyHex: event.pubkey, geohash: gh)
+        participantTracker.recordParticipant(pubkeyHex: event.pubkey, geohash: gh)
         
         // Notify only on rising-edge: previously zero people, now someone sends a chat
         let content = event.content.trimmingCharacters(in: .whitespacesAndNewlines)
@@ -3229,7 +3180,7 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
                             NostrRelayManager.shared.sendEvent(event, to: targetRelays)
                         }
                         // Track ourselves as active participant
-                        self.recordGeoParticipant(pubkeyHex: identity.publicKeyHex)
+                        self.participantTracker.recordParticipant(pubkeyHex: identity.publicKeyHex)
                     } catch {
                         SecureLogger.error("❌ Failed to send geohash screenshot message: \(error)", category: .session)
                         self.addSystemMessage(
@@ -4242,6 +4193,46 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, CommandContextProv
         return Color(peerSeed: message.sender.lowercased(), isDark: isDark)
     }
 
+    // MARK: - MessageFormattingContext Protocol
+
+    @MainActor
+    func isSelfMessage(_ message: BitchatMessage) -> Bool {
+        if let spid = message.senderPeerID {
+            // In geohash channels, compare against our per-geohash nostr short ID
+            if case .location(let ch) = activeChannel, spid.isGeoChat {
+                let myGeo: NostrIdentity? = {
+                    if let cached = cachedGeohashIdentity, cached.geohash == ch.geohash {
+                        return cached.identity
+                    }
+                    // Derive and cache
+                    if let identity = try? idBridge.deriveIdentity(forGeohash: ch.geohash) {
+                        cachedGeohashIdentity = (ch.geohash, identity)
+                        return identity
+                    }
+                    return nil
+                }()
+                if let myGeo {
+                    return spid == PeerID(nostr: myGeo.publicKeyHex)
+                }
+            }
+            return spid == meshService.myPeerID
+        }
+        // Fallback by nickname
+        if message.sender == nickname { return true }
+        if message.sender.hasPrefix(nickname + "#") { return true }
+        return false
+    }
+
+    @MainActor
+    func senderColor(for message: BitchatMessage, isDark: Bool) -> Color {
+        return peerColor(for: message, isDark: isDark)
+    }
+
+    @MainActor
+    func peerURL(for peerID: PeerID) -> URL? {
+        return URL(string: "bitchat://user/\(peerID.toPercentEncoded())")
+    }
+
     // Public helpers for views to color peers consistently in lists
     @MainActor
     func colorForNostrPubkey(_ pubkeyHexLowercased: String, isDark: Bool) -> Color {
diff --git a/bitchatTests/GeohashParticipantTrackerTests.swift b/bitchatTests/GeohashParticipantTrackerTests.swift
new file mode 100644
index 00000000..d05b8171
--- /dev/null
+++ b/bitchatTests/GeohashParticipantTrackerTests.swift
@@ -0,0 +1,293 @@
+//
+// GeohashParticipantTrackerTests.swift
+// bitchatTests
+//
+// Tests for GeohashParticipantTracker.
+// This is free and unencumbered software released into the public domain.
+//
+
+import Testing
+import Foundation
+@testable import bitchat
+
+/// Mock context for testing
+@MainActor
+final class MockParticipantContext: GeohashParticipantContext {
+    var blockedPubkeys: Set<String> = []
+    var nicknameMap: [String: String] = [:]
+    var selfPubkey: String?
+
+    func displayNameForPubkey(_ pubkeyHex: String) -> String {
+        let suffix = String(pubkeyHex.suffix(4))
+        if let self = selfPubkey, pubkeyHex.lowercased() == self.lowercased() {
+            return "me#\(suffix)"
+        }
+        if let nick = nicknameMap[pubkeyHex.lowercased()] {
+            return "\(nick)#\(suffix)"
+        }
+        return "anon#\(suffix)"
+    }
+
+    func isBlocked(_ pubkeyHexLowercased: String) -> Bool {
+        blockedPubkeys.contains(pubkeyHexLowercased.lowercased())
+    }
+}
+
+@MainActor
+struct GeohashParticipantTrackerTests {
+
+    // MARK: - Basic Recording Tests
+
+    @Test func recordParticipant_addsToActiveGeohash() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+        tracker.setActiveGeohash("abc123")
+
+        tracker.recordParticipant(pubkeyHex: "deadbeef1234")
+
+        #expect(tracker.participantCount(for: "abc123") == 1)
+    }
+
+    @Test func recordParticipant_noActiveGeohash_noOp() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+        // No active geohash set
+
+        tracker.recordParticipant(pubkeyHex: "deadbeef1234")
+
+        // Should not throw or crash
+        #expect(tracker.participantCount(for: "abc123") == 0)
+    }
+
+    @Test func recordParticipant_specificGeohash() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+
+        tracker.recordParticipant(pubkeyHex: "pubkey1", geohash: "geo1")
+        tracker.recordParticipant(pubkeyHex: "pubkey2", geohash: "geo2")
+
+        #expect(tracker.participantCount(for: "geo1") == 1)
+        #expect(tracker.participantCount(for: "geo2") == 1)
+    }
+
+    @Test func recordParticipant_updatesLastSeen() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+        tracker.setActiveGeohash("abc123")
+
+        tracker.recordParticipant(pubkeyHex: "pubkey1")
+        // Small delay and record again
+        try? await Task.sleep(nanoseconds: 10_000_000) // 10ms
+        tracker.recordParticipant(pubkeyHex: "pubkey1")
+
+        // Should still count as 1 participant (updated, not duplicated)
+        #expect(tracker.participantCount(for: "abc123") == 1)
+    }
+
+    @Test func recordParticipant_lowercasesPubkey() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+        tracker.setActiveGeohash("abc123")
+
+        tracker.recordParticipant(pubkeyHex: "DEADBEEF")
+        tracker.recordParticipant(pubkeyHex: "deadbeef")
+
+        // Should be treated as same participant
+        #expect(tracker.participantCount(for: "abc123") == 1)
+    }
+
+    // MARK: - Visible People Tests
+
+    @Test func getVisiblePeople_returnsActiveGeohashParticipants() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+        tracker.setActiveGeohash("abc123")
+
+        tracker.recordParticipant(pubkeyHex: "pubkey1")
+        tracker.recordParticipant(pubkeyHex: "pubkey2")
+
+        let people = tracker.getVisiblePeople()
+        #expect(people.count == 2)
+    }
+
+    @Test func getVisiblePeople_excludesBlockedParticipants() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        context.blockedPubkeys = ["pubkey2"]
+        tracker.configure(context: context)
+        tracker.setActiveGeohash("abc123")
+
+        tracker.recordParticipant(pubkeyHex: "pubkey1")
+        tracker.recordParticipant(pubkeyHex: "pubkey2")
+
+        let people = tracker.getVisiblePeople()
+        #expect(people.count == 1)
+        #expect(people.first?.id == "pubkey1")
+    }
+
+    @Test func getVisiblePeople_usesDisplayNameFromContext() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        context.nicknameMap = ["pubkey1234": "alice"]
+        tracker.configure(context: context)
+        tracker.setActiveGeohash("abc123")
+
+        tracker.recordParticipant(pubkeyHex: "pubkey1234")
+
+        let people = tracker.getVisiblePeople()
+        #expect(people.count == 1)
+        #expect(people.first?.displayName == "alice#1234")
+    }
+
+    @Test func getVisiblePeople_sortedByLastSeen() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+        tracker.setActiveGeohash("abc123")
+
+        tracker.recordParticipant(pubkeyHex: "older")
+        try? await Task.sleep(nanoseconds: 10_000_000) // 10ms
+        tracker.recordParticipant(pubkeyHex: "newer")
+
+        let people = tracker.getVisiblePeople()
+        #expect(people.count == 2)
+        #expect(people.first?.id == "newer")
+        #expect(people.last?.id == "older")
+    }
+
+    @Test func getVisiblePeople_emptyWhenNoActiveGeohash() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+
+        tracker.recordParticipant(pubkeyHex: "pubkey1", geohash: "abc123")
+
+        let people = tracker.getVisiblePeople()
+        #expect(people.isEmpty)
+    }
+
+    // MARK: - Activity Cutoff Tests
+
+    @Test func participantCount_excludesExpiredEntries() async {
+        // Use a very short cutoff for testing
+        let tracker = GeohashParticipantTracker(activityCutoff: -0.05) // 50ms cutoff
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+        tracker.setActiveGeohash("abc123")
+
+        tracker.recordParticipant(pubkeyHex: "pubkey1")
+
+        // Should be counted immediately
+        #expect(tracker.participantCount(for: "abc123") == 1)
+
+        // Wait for expiry
+        try? await Task.sleep(nanoseconds: 100_000_000) // 100ms
+
+        // Should be expired now
+        #expect(tracker.participantCount(for: "abc123") == 0)
+    }
+
+    // MARK: - Remove Participant Tests
+
+    @Test func removeParticipant_removesFromAllGeohashes() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+
+        tracker.recordParticipant(pubkeyHex: "pubkey1", geohash: "geo1")
+        tracker.recordParticipant(pubkeyHex: "pubkey1", geohash: "geo2")
+        tracker.recordParticipant(pubkeyHex: "pubkey2", geohash: "geo1")
+
+        tracker.removeParticipant(pubkeyHex: "pubkey1")
+
+        #expect(tracker.participantCount(for: "geo1") == 1)
+        #expect(tracker.participantCount(for: "geo2") == 0)
+    }
+
+    // MARK: - Clear Tests
+
+    @Test func clear_removesAllData() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+        tracker.setActiveGeohash("abc123")
+
+        tracker.recordParticipant(pubkeyHex: "pubkey1")
+        tracker.recordParticipant(pubkeyHex: "pubkey2", geohash: "other")
+
+        tracker.clear()
+
+        #expect(tracker.participantCount(for: "abc123") == 0)
+        #expect(tracker.participantCount(for: "other") == 0)
+        #expect(tracker.visiblePeople.isEmpty)
+    }
+
+    @Test func clearGeohash_removesOnlySpecificGeohash() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+
+        tracker.recordParticipant(pubkeyHex: "pubkey1", geohash: "geo1")
+        tracker.recordParticipant(pubkeyHex: "pubkey2", geohash: "geo2")
+
+        tracker.clear(geohash: "geo1")
+
+        #expect(tracker.participantCount(for: "geo1") == 0)
+        #expect(tracker.participantCount(for: "geo2") == 1)
+    }
+
+    // MARK: - Set Active Geohash Tests
+
+    @Test func setActiveGeohash_clearsVisiblePeopleWhenNil() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+        tracker.setActiveGeohash("abc123")
+        tracker.recordParticipant(pubkeyHex: "pubkey1")
+
+        #expect(!tracker.visiblePeople.isEmpty)
+
+        tracker.setActiveGeohash(nil)
+
+        #expect(tracker.visiblePeople.isEmpty)
+    }
+
+    @Test func setActiveGeohash_refreshesVisiblePeople() async {
+        let tracker = GeohashParticipantTracker()
+        let context = MockParticipantContext()
+        tracker.configure(context: context)
+
+        // Pre-populate a geohash
+        tracker.recordParticipant(pubkeyHex: "pubkey1", geohash: "abc123")
+
+        // Set it as active
+        tracker.setActiveGeohash("abc123")
+
+        #expect(tracker.visiblePeople.count == 1)
+    }
+
+    // MARK: - GeoPerson Tests
+
+    @Test func geoPerson_identifiable() async {
+        let person1 = GeoPerson(id: "abc", displayName: "alice", lastSeen: Date())
+        let person2 = GeoPerson(id: "abc", displayName: "alice", lastSeen: Date())
+        let person3 = GeoPerson(id: "xyz", displayName: "bob", lastSeen: Date())
+
+        #expect(person1.id == person2.id)
+        #expect(person1.id != person3.id)
+    }
+
+    @Test func geoPerson_equatable() async {
+        let date = Date()
+        let person1 = GeoPerson(id: "abc", displayName: "alice", lastSeen: date)
+        let person2 = GeoPerson(id: "abc", displayName: "alice", lastSeen: date)
+
+        #expect(person1 == person2)
+    }
+}
diff --git a/bitchatTests/MessageFormattingEngineTests.swift b/bitchatTests/MessageFormattingEngineTests.swift
new file mode 100644
index 00000000..3de0b95f
--- /dev/null
+++ b/bitchatTests/MessageFormattingEngineTests.swift
@@ -0,0 +1,223 @@
+//
+// MessageFormattingEngineTests.swift
+// bitchatTests
+//
+// Tests for MessageFormattingEngine regex patterns and utility functions.
+// This is free and unencumbered software released into the public domain.
+//
+
+import Testing
+import Foundation
+import SwiftUI
+@testable import bitchat
+
+struct MessageFormattingEngineTests {
+
+    // MARK: - Mention Extraction Tests
+
+    @Test func extractMentions_singleMention() {
+        let content = "Hello @alice how are you?"
+        let mentions = MessageFormattingEngine.extractMentions(from: content)
+        #expect(mentions == ["alice"])
+    }
+
+    @Test func extractMentions_multipleMentions() {
+        let content = "@alice and @bob are chatting with @charlie"
+        let mentions = MessageFormattingEngine.extractMentions(from: content)
+        #expect(mentions.count == 3)
+        #expect(mentions.contains("alice"))
+        #expect(mentions.contains("bob"))
+        #expect(mentions.contains("charlie"))
+    }
+
+    @Test func extractMentions_mentionWithSuffix() {
+        let content = "Hey @alice#a1b2 check this out"
+        let mentions = MessageFormattingEngine.extractMentions(from: content)
+        #expect(mentions == ["alice#a1b2"])
+    }
+
+    @Test func extractMentions_noMentions() {
+        let content = "Just a regular message with no mentions"
+        let mentions = MessageFormattingEngine.extractMentions(from: content)
+        #expect(mentions.isEmpty)
+    }
+
+    @Test func extractMentions_unicodeNickname() {
+        let content = "Hello @日本語 and @émile"
+        let mentions = MessageFormattingEngine.extractMentions(from: content)
+        #expect(mentions.count == 2)
+        #expect(mentions.contains("日本語"))
+        #expect(mentions.contains("émile"))
+    }
+
+    @Test func extractMentions_mentionWithUnderscore() {
+        let content = "Thanks @user_name_123"
+        let mentions = MessageFormattingEngine.extractMentions(from: content)
+        #expect(mentions == ["user_name_123"])
+    }
+
+    @Test func extractMentions_emailNotCaptured() {
+        // Email addresses should not be captured as mentions
+        let content = "Contact me at test@example.com"
+        let mentions = MessageFormattingEngine.extractMentions(from: content)
+        // The regex will capture "example" after @ in email - this is expected behavior
+        // as the regex doesn't distinguish email addresses
+        #expect(mentions.count == 1)
+    }
+
+    // MARK: - Cashu Token Detection Tests
+
+    @Test func containsCashuToken_validTokenA() {
+        let content = "Here's a token: cashuAeyJwcm9vZnMiOiJIZWxsbyBXb3JsZCEgVGhpcyBpcyBhIHRlc3QgdG9rZW4i"
+        #expect(MessageFormattingEngine.containsCashuToken(content))
+    }
+
+    @Test func containsCashuToken_validTokenB() {
+        let content = "Payment: cashuBeyJwcm9vZnMiOiJIZWxsbyBXb3JsZCEgVGhpcyBpcyBhIHRlc3QgdG9rZW4i"
+        #expect(MessageFormattingEngine.containsCashuToken(content))
+    }
+
+    @Test func containsCashuToken_noToken() {
+        let content = "Just a regular message about cashews"
+        #expect(!MessageFormattingEngine.containsCashuToken(content))
+    }
+
+    @Test func containsCashuToken_tooShort() {
+        let content = "Invalid: cashuAshort"
+        #expect(!MessageFormattingEngine.containsCashuToken(content))
+    }
+
+    // MARK: - Regex Pattern Tests
+
+    @Test func hashtagPattern_standaloneHashtag() {
+        let content = "#bitcoin is great"
+        let nsContent = content as NSString
+        let range = NSRange(location: 0, length: nsContent.length)
+        let matches = MessageFormattingEngine.Patterns.hashtag.matches(in: content, options: [], range: range)
+        #expect(matches.count == 1)
+    }
+
+    @Test func hashtagPattern_multipleHashtags() {
+        let content = "#bitcoin #lightning #nostr"
+        let nsContent = content as NSString
+        let range = NSRange(location: 0, length: nsContent.length)
+        let matches = MessageFormattingEngine.Patterns.hashtag.matches(in: content, options: [], range: range)
+        #expect(matches.count == 3)
+    }
+
+    @Test func hashtagPattern_hashInMiddleOfWord() {
+        let content = "test#notahashtag"
+        let nsContent = content as NSString
+        let range = NSRange(location: 0, length: nsContent.length)
+        let matches = MessageFormattingEngine.Patterns.hashtag.matches(in: content, options: [], range: range)
+        // This will match because the regex doesn't check for word boundaries
+        #expect(matches.count == 1)
+    }
+
+    @Test func bolt11Pattern_mainnet() {
+        let content = "Pay this: lnbc10u1pjexampleinvoice0000000000000000000000000000000000000000000"
+        let nsContent = content as NSString
+        let range = NSRange(location: 0, length: nsContent.length)
+        let matches = MessageFormattingEngine.Patterns.bolt11.matches(in: content, options: [], range: range)
+        #expect(matches.count == 1)
+    }
+
+    @Test func bolt11Pattern_testnet() {
+        let content = "Test: lntb10u1pjexampleinvoice0000000000000000000000000000000000000000000"
+        let nsContent = content as NSString
+        let range = NSRange(location: 0, length: nsContent.length)
+        let matches = MessageFormattingEngine.Patterns.bolt11.matches(in: content, options: [], range: range)
+        #expect(matches.count == 1)
+    }
+
+    @Test func lnurlPattern_valid() {
+        let content = "LNURL: lnurl1dp68gurn8ghj7um9wfmxjcm99e3k7mf0v9cxj0m385ekvcenxc6r2c35xvukxefcv5mkvv34x5ekzd3ev56nyd3hxqurzepexejxxepnxscrvwfnv9nxzcn9xq6xyefhvgcxxcmyxymnserx"
+        let nsContent = content as NSString
+        let range = NSRange(location: 0, length: nsContent.length)
+        let matches = MessageFormattingEngine.Patterns.lnurl.matches(in: content, options: [], range: range)
+        #expect(matches.count == 1)
+    }
+
+    @Test func lightningSchemePattern_valid() {
+        let content = "Click: lightning:lnbc10u1example"
+        let nsContent = content as NSString
+        let range = NSRange(location: 0, length: nsContent.length)
+        let matches = MessageFormattingEngine.Patterns.lightningScheme.matches(in: content, options: [], range: range)
+        #expect(matches.count == 1)
+    }
+
+    @Test func cashuPattern_valid() {
+        let content = "Token: cashuAeyJwcm9vZnMiOlt7ImlkIjoiMDAwMDAwMDAwMDAwMDAwMCJ9XX0="
+        let nsContent = content as NSString
+        let range = NSRange(location: 0, length: nsContent.length)
+        let matches = MessageFormattingEngine.Patterns.cashu.matches(in: content, options: [], range: range)
+        #expect(matches.count == 1)
+    }
+
+    // MARK: - URL Detection Tests
+
+    @Test func linkDetector_httpURL() {
+        let content = "Check out http://example.com"
+        let nsContent = content as NSString
+        let range = NSRange(location: 0, length: nsContent.length)
+        let matches = MessageFormattingEngine.Patterns.linkDetector?.matches(in: content, options: [], range: range) ?? []
+        #expect(matches.count == 1)
+    }
+
+    @Test func linkDetector_httpsURL() {
+        let content = "Visit https://example.com/path?query=value"
+        let nsContent = content as NSString
+        let range = NSRange(location: 0, length: nsContent.length)
+        let matches = MessageFormattingEngine.Patterns.linkDetector?.matches(in: content, options: [], range: range) ?? []
+        #expect(matches.count == 1)
+    }
+
+    @Test func linkDetector_multipleURLs() {
+        let content = "See https://a.com and http://b.com"
+        let nsContent = content as NSString
+        let range = NSRange(location: 0, length: nsContent.length)
+        let matches = MessageFormattingEngine.Patterns.linkDetector?.matches(in: content, options: [], range: range) ?? []
+        #expect(matches.count == 2)
+    }
+
+    // MARK: - String Extension Tests
+
+    @Test func splitSuffix_withSuffix() {
+        let name = "alice#a1b2"
+        let (base, suffix) = name.splitSuffix()
+        #expect(base == "alice")
+        #expect(suffix == "#a1b2")
+    }
+
+    @Test func splitSuffix_withoutSuffix() {
+        let name = "alice"
+        let (base, suffix) = name.splitSuffix()
+        #expect(base == "alice")
+        #expect(suffix == "")
+    }
+
+    @Test func splitSuffix_withAtPrefix() {
+        let name = "@alice#a1b2"
+        let (base, suffix) = name.splitSuffix()
+        #expect(base == "alice")
+        #expect(suffix == "#a1b2")
+    }
+
+    @Test func hasVeryLongToken_noLongToken() {
+        let content = "Short words only here"
+        #expect(!content.hasVeryLongToken(threshold: 50))
+    }
+
+    @Test func hasVeryLongToken_withLongToken() {
+        let longToken = String(repeating: "a", count: 100)
+        let content = "Here is a \(longToken) token"
+        #expect(content.hasVeryLongToken(threshold: 50))
+    }
+
+    @Test func hasVeryLongToken_exactThreshold() {
+        let exactToken = String(repeating: "a", count: 50)
+        let content = "Token: \(exactToken)"
+        // Exactly at threshold DOES trigger (uses >= comparison)
+        #expect(content.hasVeryLongToken(threshold: 50))
+    }
+}