improvement(chat): stop reloading the full transcript on every turn and event

apps/sim/app/api/v2/chat/route.test.ts

@@ -267,7 +267,6 @@ describe('POST /api/v2/chat', () => {
     mockResolveOrCreateChat.mockResolvedValue({
       chatId: SERVER_ISSUED_CHAT_ID,
       chat: chatRow(SERVER_ISSUED_CHAT_ID),
-      conversationHistory: [],
       isNew: true,
     })
   })
@@ -444,7 +443,6 @@ describe('POST /api/v2/chat', () => {
     mockResolveOrCreateChat.mockResolvedValue({
       chatId: OWNED_CONVERSATION_ID,
       chat: chatRow(OWNED_CONVERSATION_ID),
-      conversationHistory: [],
       isNew: false,
     })
 
@@ -469,38 +467,10 @@ describe('POST /api/v2/chat', () => {
     })
   })
 
-  it('posts only the current turn on a resumed conversation, never the stored transcript', async () => {
-    mockResolveOrCreateChat.mockResolvedValue({
-      chatId: OWNED_CONVERSATION_ID,
-      chat: chatRow(OWNED_CONVERSATION_ID),
-      conversationHistory: [
-        { role: 'user', content: 'first' },
-        { role: 'assistant', content: 'first reply' },
-      ],
-      isNew: false,
-    })
-
-    const response = await callChat({
-      workspaceId: 'workspace-1',
-      message: 'and then?',
-      conversationId: OWNED_CONVERSATION_ID,
-    })
-
-    expect(response.status).toBe(200)
-    // Continuity is keyed by chatId downstream, exactly as the web send path
-    // and the Sim Chat block do. Replaying the transcript here would duplicate
-    // every prior turn.
-    expect(mockRunHeadlessCopilotLifecycle.mock.calls[0][0]).toMatchObject({
-      message: 'and then?',
-      chatId: OWNED_CONVERSATION_ID,
-    })
-  })
-
   it('answers 404 and runs nothing when the resolver refuses the named conversation', async () => {
     mockResolveOrCreateChat.mockResolvedValue({
       chatId: OWNED_CONVERSATION_ID,
       chat: null,
-      conversationHistory: [],
       isNew: false,
     })
 

apps/sim/app/api/v2/chat/route.ts

@@ -264,12 +264,11 @@ export const POST = withRouteHandler(
       // surface uses, and refuse every id that does not resolve with the same
       // response so the refusal carries no information about the id. Omitting
       // the id mints a server-issued conversation instead of trusting one.
-      // The resolved transcript is deliberately not forwarded: continuity is
-      // keyed by `chatId` downstream, exactly as the web send path and the Sim
-      // Chat block do, both of which post a single message with a chat id.
+      // Continuity is keyed by `chatId` downstream, exactly as the web send
+      // path and the Sim Chat block do, both of which post a single message
+      // with a chat id.
       const resolvedChat = await resolveOrCreateChat({
         ...(conversationId ? { chatId: conversationId } : {}),
-        includeTranscript: false,
         userId,
         workspaceId,
         model: MOTHERSHIP_CHAT_DEFAULT_MODEL,

apps/sim/app/workspace/[workspaceId]/home/hooks/use-chat.dom.test.tsx

@@ -82,6 +82,7 @@ import {
 } from '@/app/workspace/[workspaceId]/home/hooks/send-handoff'
 import { useChat } from '@/app/workspace/[workspaceId]/home/hooks/use-chat'
 import { type MothershipChatHistory, mothershipChatKeys } from '@/hooks/queries/mothership-chats'
+import { handleMothershipChatStatusEvent } from '@/hooks/use-mothership-chat-events'
 import { useExecutionStore } from '@/stores/execution/store'
 import { useMothershipQueueStore } from '@/stores/mothership-queue/store'
 
@@ -1821,4 +1822,81 @@ describe('useChat remount send recovery', () => {
     expect(getResult().messageQueue.map((entry) => entry.id)).toEqual(['unsent-entry'])
     expect(state.postBodies).toHaveLength(0)
   })
+
+  it('loads the saved transcript once when its own stream completes', async () => {
+    const chatId = 'chat-own-completion'
+    const history: MothershipChatHistory = {
+      id: chatId,
+      mode: 'agent',
+      title: 'Own stream',
+      messages: [],
+      activeStreamId: null,
+      resources: [],
+    }
+    const saved = [
+      { id: 'saved-user', role: 'user', content: 'Summarize the run' },
+      { id: 'saved-assistant', role: 'assistant', content: 'Done.' },
+    ]
+    const detailRequests: string[] = []
+    mockRequestJson.mockImplementation((contract: AnyApiRouteContract) => {
+      if (contract.path !== '/api/mothership/chats/[chatId]') {
+        return Promise.resolve({ chats: [] })
+      }
+      detailRequests.push(chatId)
+      return Promise.resolve({ chat: { ...history, messages: saved } })
+    })
+    let stream: ReadableStreamDefaultController<Uint8Array> | undefined
+    let streamId: string | undefined
+    const emit = (event: Omit<MothershipStreamV1EventEnvelope, 'v' | 'ts' | 'stream'>) =>
+      stream?.enqueue(
+        new TextEncoder().encode(
+          `data: ${JSON.stringify({ v: 1, ts: '', stream: { streamId }, ...event })}\n\n`
+        )
+      )
+    vi.stubGlobal('fetch', async (input: RequestInfo | URL, init?: RequestInit) => {
+      if (String(input) !== '/api/mothership/chat' || init?.method !== 'POST') {
+        return fetchStub(input, init)
+      }
+      streamId = JSON.parse(String(init.body)).userMessageId
+      return new Response(
+        new ReadableStream<Uint8Array>({
+          start(controller) {
+            stream = controller
+          },
+        }),
+        { headers: { 'Content-Type': 'text/event-stream', 'x-mothership-chat-id': chatId } }
+      )
+    })
+    const { getResult } = renderUseChatInChat(chatId, history)
+
+    await act(async () => {
+      void getResult().sendMessage('Summarize the run')
+    })
+    await waitFor(() => stream !== undefined)
+    emit({ seq: 1, type: 'text', payload: { channel: 'assistant', text: 'Done.' } })
+    await waitFor(
+      () =>
+        queryClient.getQueryData<MothershipChatHistory>(mothershipChatKeys.detail(chatId))
+          ?.activeStreamId === streamId
+    )
+    /** The server publishes `completed` after persisting and before closing the stream. */
+    handleMothershipChatStatusEvent(queryClient, 'ws-1', {
+      chatId,
+      type: 'completed',
+      streamId,
+    })
+    emit({ seq: 2, type: 'complete', payload: { status: 'complete' } })
+    stream?.close()
+
+    await waitFor(() => !getResult().isSending && detailRequests.length > 0)
+    await act(async () => {
+      await sleep(50)
+    })
+    expect(detailRequests).toHaveLength(1)
+    expect(
+      queryClient
+        .getQueryData<MothershipChatHistory>(mothershipChatKeys.detail(chatId))
+        ?.messages.map((message) => message.id)
+    ).toEqual(['saved-user', 'saved-assistant'])
+  })
 })

apps/sim/hooks/use-mothership-chat-events.test.ts

@@ -1,4 +1,5 @@
-import type { QueryClient } from '@tanstack/react-query'
+import { sleep } from '@sim/utils/helpers'
+import { QueryClient, QueryObserver } from '@tanstack/react-query'
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 const { suspendBrowserScope, suspendTerminalScope } = vi.hoisted(() => ({
@@ -9,7 +10,7 @@ const { suspendBrowserScope, suspendTerminalScope } = vi.hoisted(() => ({
 vi.mock('@/lib/browser-agent/transport', () => ({ suspendBrowserScope }))
 vi.mock('@/lib/terminal/transport', () => ({ suspendTerminalScope }))
 
-import { mothershipChatKeys } from '@/hooks/queries/mothership-chats'
+import { type MothershipChatHistory, mothershipChatKeys } from '@/hooks/queries/mothership-chats'
 import {
   handleMothershipChatStatusEvent,
   resyncMothershipChatCaches,
@@ -184,6 +185,80 @@ describe('handleMothershipChatStatusEvent', () => {
   )
 })
 
+describe('chat detail refetches driven by status events', () => {
+  function mountDetail(cached: MothershipChatHistory) {
+    const queryClient = new QueryClient()
+    const fetchTranscript = vi.fn(async () => cached)
+    queryClient.setQueryData(mothershipChatKeys.detail('chat-1'), cached)
+    const unsubscribe = new QueryObserver(queryClient, {
+      queryKey: mothershipChatKeys.detail('chat-1'),
+      queryFn: fetchTranscript,
+      staleTime: Number.POSITIVE_INFINITY,
+    }).subscribe(() => {})
+    return { queryClient, fetchTranscript, unsubscribe }
+  }
+
+  const liveStream: MothershipChatHistory = {
+    id: 'chat-1',
+    title: null,
+    messages: [
+      { id: 'stream-1' },
+      { id: 'live-assistant:stream-1' },
+    ] as MothershipChatHistory['messages'],
+    activeStreamId: 'stream-1',
+    resources: [],
+  }
+
+  it('does not reload the transcript when the viewer finishes its own live stream', async () => {
+    const { queryClient, fetchTranscript, unsubscribe } = mountDetail(liveStream)
+
+    handleMothershipChatStatusEvent(queryClient, 'ws-1', {
+      chatId: 'chat-1',
+      type: 'completed',
+      streamId: 'stream-1',
+    })
+    await sleep(0)
+
+    expect(fetchTranscript).not.toHaveBeenCalled()
+    unsubscribe()
+  })
+
+  it('reloads the saved transcript when a cached mid-stream detail is opened after completion', async () => {
+    const queryClient = new QueryClient()
+    const fetchTranscript = vi.fn(async () => ({ ...liveStream, activeStreamId: null }))
+    queryClient.setQueryData(mothershipChatKeys.detail('chat-1'), liveStream)
+
+    handleMothershipChatStatusEvent(queryClient, 'ws-1', {
+      chatId: 'chat-1',
+      type: 'completed',
+      streamId: 'stream-1',
+    })
+    const unsubscribe = new QueryObserver(queryClient, {
+      queryKey: mothershipChatKeys.detail('chat-1'),
+      queryFn: fetchTranscript,
+      staleTime: Number.POSITIVE_INFINITY,
+    }).subscribe(() => {})
+
+    await vi.waitFor(() => expect(fetchTranscript).toHaveBeenCalledTimes(1))
+    unsubscribe()
+  })
+
+  it('marks the detail stale on rename without reloading the transcript', async () => {
+    const { queryClient, fetchTranscript, unsubscribe } = mountDetail({
+      ...liveStream,
+      messages: [],
+      activeStreamId: null,
+    })
+
+    handleMothershipChatStatusEvent(queryClient, 'ws-1', { chatId: 'chat-1', type: 'renamed' })
+    await sleep(0)
+
+    expect(fetchTranscript).not.toHaveBeenCalled()
+    expect(queryClient.getQueryState(mothershipChatKeys.detail('chat-1'))?.isInvalidated).toBe(true)
+    unsubscribe()
+  })
+})
+
 describe('resyncMothershipChatCaches', () => {
   const queryClient = {
     invalidateQueries: vi.fn().mockResolvedValue(undefined),

apps/sim/hooks/use-mothership-chat-events.ts

@@ -33,12 +33,6 @@ interface ChatStatusEventPayload {
   streamId?: string
 }
 
-const DETAIL_INVALIDATING_CHAT_STATUS_TYPES = new Set<ChatStatusEventType>([
-  'started',
-  'completed',
-  'renamed',
-])
-
 function isChatStatusEventType(value: unknown): value is ChatStatusEventType {
   return typeof value === 'string' && CHAT_STATUS_TYPE_SET.has(value)
 }
@@ -69,7 +63,6 @@ function shouldSkipDetailInvalidationForStreamEvent(
   current: MothershipChatHistory | undefined,
   payload: ChatStatusEventPayload
 ) {
-  if (payload.type !== 'started' && payload.type !== 'completed') return false
   if (!current?.activeStreamId) return false
   if (!payload.streamId) return isLocalOptimisticActiveStream(current)
   if (payload.type === 'started' && current.activeStreamId === payload.streamId) return true
@@ -128,17 +121,37 @@ export function handleMothershipChatStatusEvent(
     queryClient.removeQueries({ queryKey: mothershipChatKeys.detail(payload.chatId) })
     return
   }
-  if (payload.type === 'started' || payload.type === 'completed') {
-    const current = queryClient.getQueryData<MothershipChatHistory>(
-      mothershipChatKeys.detail(payload.chatId)
-    )
-    if (shouldSkipDetailInvalidationForStreamEvent(current, payload)) {
-      return
-    }
-  }
-  if (payload.type && DETAIL_INVALIDATING_CHAT_STATUS_TYPES.has(payload.type)) {
-    queryClient.invalidateQueries({ queryKey: mothershipChatKeys.detail(payload.chatId) })
+  if (payload.type === 'renamed') {
+    /**
+     * The lists invalidated above carry the title every surface renders; the
+     * detail only needs marking stale, not a full transcript reload.
+     */
+    queryClient.invalidateQueries({
+      queryKey: mothershipChatKeys.detail(payload.chatId),
+      refetchType: 'none',
+    })
+    return
   }
+  if (payload.type !== 'started' && payload.type !== 'completed') return
+  const current = queryClient.getQueryData<MothershipChatHistory>(
+    mothershipChatKeys.detail(payload.chatId)
+  )
+  if (shouldSkipDetailInvalidationForStreamEvent(current, payload)) return
+  /**
+   * A completion of the cached live stream only marks the detail stale. The
+   * server persists the turn before closing the stream, so a surface rendering
+   * it refetches through its own finalization; the live message alone cannot
+   * tell this tab's stream from a server-loaded mid-stream snapshot, so any
+   * other cached copy reloads the saved transcript on its next mount.
+   */
+  const completesCachedLiveStream =
+    payload.type === 'completed' &&
+    current?.activeStreamId === payload.streamId &&
+    isLocalOptimisticActiveStream(current)
+  queryClient.invalidateQueries({
+    queryKey: mothershipChatKeys.detail(payload.chatId),
+    ...(completesCachedLiveStream ? { refetchType: 'none' as const } : {}),
+  })
 }
 
 /**