Fix iOS chat scroll pinning

ios/Packages/Sybil/Sources/Sybil/SybilChatTranscriptView.swift

@@ -7,38 +7,55 @@ struct SybilChatTranscriptView: View {
     var isSending: Bool
     var topContentInset: CGFloat = 0
     var bottomContentInset: CGFloat = 0
+    var bottomPinRequestID: Int = 0
 
-    private var hasPendingAssistant: Bool {
-        messages.contains { message in
-            message.id.hasPrefix("temp-assistant-") && message.content.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty
-        }
-    }
+    private let bottomAnchorID = "sybil-chat-transcript-bottom-anchor"
 
     var body: some View {
+        ScrollViewReader { proxy in
             ScrollView {
                 LazyVStack(alignment: .leading, spacing: 26) {
-                ForEach(messages.reversed()) { message in
-                    MessageBubble(message: message, isSending: isSending)
-                        .frame(maxWidth: .infinity)
-                        .scaleEffect(x: 1, y: -1)
-                }
-
                     if isLoading && messages.isEmpty {
                         Text("Loading messages…")
                             .font(.sybil(.footnote))
                             .foregroundStyle(SybilTheme.textMuted)
                             .padding(.top, 24)
-                        .scaleEffect(x: 1, y: -1)
                     }
+
+                    ForEach(messages) { message in
+                        MessageBubble(message: message, isSending: isSending)
+                            .frame(maxWidth: .infinity)
+                    }
+
+                    Color.clear
+                        .frame(height: 18 + bottomContentInset)
+                        .id(bottomAnchorID)
                 }
                 .frame(maxWidth: .infinity, alignment: .leading)
                 .padding(.horizontal, 14)
-            .padding(.top, 18 + bottomContentInset)
-            .padding(.bottom, 18 + topContentInset)
+                .padding(.top, 18 + topContentInset)
             }
             .frame(maxWidth: .infinity, alignment: .leading)
             .scrollDismissesKeyboard(.interactively)
-        .scaleEffect(x: 1, y: -1)
+            .onAppear {
+                scrollToBottom(with: proxy, animated: false)
+            }
+            .onChange(of: bottomPinRequestID) { _, _ in
+                scrollToBottom(with: proxy, animated: true)
+            }
+        }
+    }
+
+    private func scrollToBottom(with proxy: ScrollViewProxy, animated: Bool) {
+        let action = {
+            proxy.scrollTo(bottomAnchorID, anchor: .bottom)
+        }
+
+        if animated {
+            withAnimation(.easeOut(duration: 0.18), action)
+        } else {
+            action()
+        }
     }
 }
 

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

@@ -107,6 +107,7 @@ final class SybilViewModel {
     var isLoadingCollections = false
     var isLoadingSelection = false
     var isCreatingSearchChat = false
+    var chatBottomPinRequestID = 0
     var errorMessage: String?
 
     var composer = ""
@@ -1699,6 +1700,10 @@ final class SybilViewModel {
         isLoadingSelection = false
     }
 
+    private func requestChatBottomPin() {
+        chatBottomPinRequestID += 1
+    }
+
     private func startSelectionRefreshTask() -> Task<Void, Never> {
         isLoadingSelection = true
         let task = Task { [weak self] in
@@ -1752,6 +1757,7 @@ final class SybilViewModel {
                     }
                     selectedChat = chat
                     selectedSearch = nil
+                    requestChatBottomPin()
 
                     if let provider = chat.lastUsedProvider,
                        let model = chat.lastUsedModel,
@@ -1824,6 +1830,7 @@ final class SybilViewModel {
         } else {
             pendingDraftChatState = PendingChatState(chatID: nil, messages: optimisticMessages)
         }
+        requestChatBottomPin()
 
         if chatID == nil {
             let created = try await client.createChat(title: nil)
@@ -1871,6 +1878,7 @@ final class SybilViewModel {
         if let draftPending = pendingDraftChatState {
             pendingDraftChatState = nil
             pendingChatStates[chatID] = PendingChatState(chatID: chatID, messages: draftPending.messages)
+            requestChatBottomPin()
         } else if pendingChatStates[chatID] == nil {
             pendingChatStates[chatID] = PendingChatState(chatID: chatID, messages: optimisticMessages)
         } else {

ios/Packages/Sybil/Sources/Sybil/SybilWorkspaceView.swift

@@ -194,7 +194,8 @@ struct SybilWorkspaceView: View {
                         isLoading: viewModel.isLoadingSelection,
                         isSending: viewModel.isSendingVisibleChat,
                         topContentInset: showsCustomWorkspaceNavigation ? customWorkspaceNavigationContentInset : 0,
-                        bottomContentInset: viewModel.showsComposer ? composerOverlayContentInset : 0
+                        bottomContentInset: viewModel.showsComposer ? composerOverlayContentInset : 0,
+                        bottomPinRequestID: viewModel.chatBottomPinRequestID
                     )
                     .id(transcriptScrollContextID)
                 }

ios/Packages/Sybil/Tests/SybilTests/SybilTests.swift

@@ -495,6 +495,7 @@ private func makeSearchDetail(id: String, date: Date, answer: String) -> SearchD
     #expect(snapshot.listSearches == 0)
     #expect(snapshot.getChat == 1)
     #expect(viewModel.selectedChat?.messages.first?.content == "refreshed transcript")
+    #expect(viewModel.chatBottomPinRequestID == 1)
 }
 
 @MainActor
@@ -682,6 +683,37 @@ private func makeSearchDetail(id: String, date: Date, answer: String) -> SearchD
     await sendTask.value
 }
 
+@MainActor
+@Test func chatBottomPinRequestDoesNotFollowAssistantStreaming() async throws {
+    let date = Date(timeIntervalSince1970: 1_700_000_245)
+    let chat = makeChatSummary(id: "chat-pin", date: date)
+    let detail = makeChatDetail(id: "chat-pin", date: date, body: "existing transcript")
+    let client = MockSybilClient(
+        chatsResponse: [chat],
+        chatDetails: ["chat-pin": detail]
+    )
+    await client.setCompletionStreamEvents([
+        .delta(CompletionStreamDelta(text: "partial ")),
+        .delta(CompletionStreamDelta(text: "response")),
+        .done(CompletionStreamDone(text: "partial response"))
+    ])
+    let viewModel = SybilViewModel(settings: testSettings(named: #function)) { _ in client }
+    viewModel.isAuthenticated = true
+    viewModel.isCheckingSession = false
+    viewModel.chats = [chat]
+    viewModel.workspaceItems = [WorkspaceItem(chat: chat)]
+    viewModel.selectedItem = .chat("chat-pin")
+    viewModel.selectedChat = detail
+    viewModel.composer = "continue"
+
+    let initialPinRequestID = viewModel.chatBottomPinRequestID
+    await viewModel.sendComposer()
+
+    let snapshot = await client.currentSnapshot()
+    #expect(snapshot.runCompletionStream == 1)
+    #expect(viewModel.chatBottomPinRequestID == initialPinRequestID + 1)
+}
+
 @MainActor
 @Test func quickQuestionRunsNonPersistentCompletionStream() async throws {
     let client = MockSybilClient()