Add chat thread forking

ios/Packages/Sybil/Sources/Sybil/SybilViewModel.swift

@@ -406,14 +406,17 @@ final class SybilViewModel {
                 } else {
                     initiatedLabel = nil
                 }
+                let starOwner = item.parentChatId.flatMap { parentChatID in
+                    workspaceItems.first(where: { $0.type == .chat && $0.id == parentChatID })
+                } ?? item
 
                 return SidebarItem(
                     selection: .chat(item.id),
                     kind: .chat,
                     title: chatTitle(title: item.title, messages: nil),
                     updatedAt: item.updatedAt,
-                    starred: item.starred,
-                    starredAt: item.starredAt,
+                    starred: starOwner.starred,
+                    starredAt: starOwner.starredAt,
                     initiatedLabel: initiatedLabel,
                     isRunning: isChatRowRunning(item.id)
                 )
@@ -687,6 +690,8 @@ final class SybilViewModel {
             selectedChat = ChatDetail(
                 id: chat.id,
                 title: chat.title,
+                parentChatId: chat.parentChatId,
+                titleGenerationPending: chat.titleGenerationPending,
                 createdAt: chat.createdAt,
                 updatedAt: chat.updatedAt,
                 starred: chat.starred,
@@ -896,7 +901,8 @@ final class SybilViewModel {
                 let client = try client()
                 switch selection {
                 case let .chat(chatID):
-                    let updated = try await client.updateChatStar(chatID: chatID, starred: starred)
+                    let rootChatID = chatFamilyRootID(for: chatID)
+                    let updated = try await client.updateChatStar(chatID: rootChatID, starred: starred)
                     applyChatSummary(updated, moveToFront: false)
                 case let .search(searchID):
                     let updated = try await client.updateSearchStar(searchID: searchID, starred: starred)
@@ -1454,6 +1460,8 @@ final class SybilViewModel {
 
         if selectedChat?.id == chat.id {
             selectedChat?.title = chat.title
+            selectedChat?.parentChatId = chat.parentChatId
+            selectedChat?.titleGenerationPending = chat.titleGenerationPending
             selectedChat?.updatedAt = chat.updatedAt
             selectedChat?.starred = chat.starred
             selectedChat?.starredAt = chat.starredAt
@@ -1505,6 +1513,19 @@ final class SybilViewModel {
         workspaceItems.insert(item, at: 0)
     }
 
+    private func chatFamilyRootID(for chatID: String) -> String {
+        if let selectedChat, selectedChat.id == chatID, let parentChatID = selectedChat.parentChatId {
+            return parentChatID
+        }
+        if let parentChatID = chats.first(where: { $0.id == chatID })?.parentChatId {
+            return parentChatID
+        }
+        if let parentChatID = workspaceItems.first(where: { $0.type == .chat && $0.id == chatID })?.parentChatId {
+            return parentChatID
+        }
+        return chatID
+    }
+
     private func attachToVisibleActiveRunIfNeeded() {
         guard draftKind == nil else {
             return
@@ -1854,6 +1875,8 @@ final class SybilViewModel {
                 selectedChat = ChatDetail(
                     id: created.id,
                     title: created.title,
+                    parentChatId: created.parentChatId,
+                    titleGenerationPending: created.titleGenerationPending,
                     createdAt: created.createdAt,
                     updatedAt: created.updatedAt,
                     starred: created.starred,
@@ -1912,7 +1935,7 @@ final class SybilViewModel {
         let streamLifecycleGeneration = appLifecycleGeneration
         let streamStartedWhileInactive = !isAppActive
 
-        if isUntitledChat(chatID: chatID, detail: currentSelectedChat) {
+        if shouldRequestChatTitle(baseChat) {
             Task { [weak self] in
                 guard let self else { return }
                 do {
@@ -2623,20 +2646,10 @@ final class SybilViewModel {
         )
     }
 
-    private func isUntitledChat(chatID: String, detail: ChatDetail?) -> Bool {
-        if let detail, detail.id == chatID {
-            if let title = detail.title?.trimmingCharacters(in: .whitespacesAndNewlines), !title.isEmpty {
-                return false
-            }
+    private func shouldRequestChatTitle(_ chat: ChatDetail) -> Bool {
+        if chat.titleGenerationPending {
             return true
         }
-
-        if let summary = chats.first(where: { $0.id == chatID }) {
-            if let title = summary.title?.trimmingCharacters(in: .whitespacesAndNewlines), !title.isEmpty {
-                return false
-            }
-        }
-
-        return true
+        return chat.title?.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty ?? true
     }
 }