feat(chat): preserve conversation history

macos/WayfinderMac/Sources/WayfinderMac/Models/ChatConversation.swift

@@ -0,0 +1,34 @@
+import Foundation
+
+public struct ChatConversation: Identifiable, Codable, Equatable, Sendable {
+    public let id: UUID
+    public var messages: [ChatMessage]
+    public let createdAt: Date
+    public var updatedAt: Date
+
+    public init(
+        id: UUID = UUID(),
+        messages: [ChatMessage] = [],
+        createdAt: Date = Date(),
+        updatedAt: Date = Date()
+    ) {
+        self.id = id
+        self.messages = messages
+        self.createdAt = createdAt
+        self.updatedAt = updatedAt
+    }
+
+    public var title: String {
+        messages.first(where: { $0.role == .user })?.text
+            .trimmingCharacters(in: .whitespacesAndNewlines)
+            .nonEmpty ?? "New chat"
+    }
+
+    public var turnCount: Int {
+        messages.filter { $0.role == .user }.count
+    }
+}
+
+private extension String {
+    var nonEmpty: String? { isEmpty ? nil : self }
+}

macos/WayfinderMac/Sources/WayfinderMac/Services/ChatConversationStore.swift

@@ -0,0 +1,64 @@
+import Foundation
+
+public final class ChatConversationStore: @unchecked Sendable {
+    private static let maximumStoredConversations = 100
+    private static let maximumFileBytes = 8 * 1_024 * 1_024
+
+    private let fileURL: URL?
+    private let fileManager: FileManager
+
+    public init(fileURL: URL? = nil, fileManager: FileManager = .default) {
+        self.fileURL = fileURL
+        self.fileManager = fileManager
+    }
+
+    public static func applicationSupport(fileManager: FileManager = .default) -> ChatConversationStore {
+        let root = fileManager.urls(for: .applicationSupportDirectory, in: .userDomainMask).first
+        return ChatConversationStore(
+            fileURL: root?
+                .appendingPathComponent("Wayfinder", isDirectory: true)
+                .appendingPathComponent("chat-history.json", isDirectory: false),
+            fileManager: fileManager
+        )
+    }
+
+    public func load() -> [ChatConversation] {
+        guard let fileURL,
+              let attributes = try? fileManager.attributesOfItem(atPath: fileURL.path),
+              let byteCount = attributes[.size] as? NSNumber,
+              byteCount.intValue <= Self.maximumFileBytes,
+              let data = try? Data(contentsOf: fileURL, options: .mappedIfSafe),
+              let conversations = try? JSONDecoder().decode([ChatConversation].self, from: data) else {
+            return []
+        }
+        return Array(
+            conversations
+                .filter { !$0.messages.isEmpty }
+                .sorted { $0.updatedAt > $1.updatedAt }
+                .prefix(Self.maximumStoredConversations)
+        )
+    }
+
+    public func save(_ conversations: [ChatConversation]) {
+        guard let fileURL else { return }
+        let bounded = Array(
+            conversations
+                .filter { !$0.messages.isEmpty }
+                .sorted { $0.updatedAt > $1.updatedAt }
+                .prefix(Self.maximumStoredConversations)
+        )
+        guard let data = try? JSONEncoder().encode(bounded),
+              data.count <= Self.maximumFileBytes else {
+            return
+        }
+        do {
+            try fileManager.createDirectory(
+                at: fileURL.deletingLastPathComponent(),
+                withIntermediateDirectories: true
+            )
+            try data.write(to: fileURL, options: [.atomic, .completeFileProtection])
+        } catch {
+            // Chat remains usable in memory if local history cannot be written.
+        }
+    }
+}

macos/WayfinderMac/Sources/WayfinderMac/State/AppState.swift

@@ -12,24 +12,37 @@ public final class AppState: ObservableObject {
     @Published public var chatDestination: ChatDestination = .automatic
     @Published public private(set) var chatDestinations: [ChatDestination] = [.automatic]
     @Published public private(set) var chatMessages: [ChatMessage]
+    @Published public private(set) var chatConversations: [ChatConversation]
+    @Published public private(set) var activeChatConversationID: UUID
     @Published public private(set) var isSendingMessage = false
     @Published public private(set) var setupAssessment: SetupAssessment = .checking
 
     public let chatDestinationNameStore: ChatDestinationNameStore
 
     private let client: any WayfinderClient
+    private let chatConversationStore: ChatConversationStore
     private let setupService = SetupService()
     private var chatTask: Task<Void, Never>?
 
     public init(
         client: any WayfinderClient,
-        chatDestinationNameStore: ChatDestinationNameStore? = nil
+        chatDestinationNameStore: ChatDestinationNameStore? = nil,
+        chatConversationStore: ChatConversationStore = ChatConversationStore()
     ) {
         self.client = client
         self.chatDestinationNameStore = chatDestinationNameStore ?? ChatDestinationNameStore()
+        self.chatConversationStore = chatConversationStore
         self.routingStats = .empty
         self.gatewayOverview = .checking
-        self.chatMessages = []
+        let storedConversations = chatConversationStore.load()
+        self.chatConversations = storedConversations
+        if let mostRecent = storedConversations.first {
+            self.activeChatConversationID = mostRecent.id
+            self.chatMessages = mostRecent.messages
+        } else {
+            self.activeChatConversationID = UUID()
+            self.chatMessages = []
+        }
     }
 
     public var canAnalyse: Bool {
@@ -139,6 +152,7 @@ public final class AppState: ObservableObject {
             text: "",
             state: .streaming
         ))
+        saveActiveConversation()
 
         chatTask = Task {
             do {
@@ -178,6 +192,7 @@ public final class AppState: ObservableObject {
                 }
                 self.isSendingMessage = false
                 self.chatTask = nil
+                self.saveActiveConversation()
                 self.refreshStats()
             } catch {
                 if Task.isCancelled || error is CancellationError {
@@ -200,11 +215,25 @@ public final class AppState: ObservableObject {
         chatTask?.cancel()
     }
 
-    public func clearChat() {
+    public func startNewChat() {
         guard canClearChat else {
             return
         }
-        chatMessages.removeAll()
+        saveActiveConversation()
+        activeChatConversationID = UUID()
+        chatMessages = []
+        chatDraft = ""
+    }
+
+    public func selectChatConversation(_ id: UUID) {
+        guard !isSendingMessage, id != activeChatConversationID,
+              let conversation = chatConversations.first(where: { $0.id == id }) else {
+            return
+        }
+        saveActiveConversation()
+        activeChatConversationID = conversation.id
+        chatMessages = conversation.messages
+        chatDraft = ""
     }
 
     public func retryLastChatTurn() {
@@ -318,6 +347,7 @@ public final class AppState: ObservableObject {
         }
         isSendingMessage = false
         chatTask = nil
+        saveActiveConversation()
     }
 
     private func finishFailedChatMessage(
@@ -332,8 +362,27 @@ public final class AppState: ObservableObject {
         }
         isSendingMessage = false
         chatTask = nil
+        saveActiveConversation()
         refreshStats()
     }
+
+    private func saveActiveConversation() {
+        guard !chatMessages.isEmpty else { return }
+        let now = Date()
+        if let index = chatConversations.firstIndex(where: { $0.id == activeChatConversationID }) {
+            chatConversations[index].messages = chatMessages
+            chatConversations[index].updatedAt = now
+        } else {
+            chatConversations.append(ChatConversation(
+                id: activeChatConversationID,
+                messages: chatMessages,
+                createdAt: chatMessages.first?.createdAt ?? now,
+                updatedAt: now
+            ))
+        }
+        chatConversations.sort { $0.updatedAt > $1.updatedAt }
+        chatConversationStore.save(chatConversations)
+    }
 }
 
 public enum SettingsSection: String, CaseIterable, Codable, Identifiable, Sendable {