Fix iOS chat scroll pinning

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()