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

Author: waleedlatif1

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/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 +185,75 @@ 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 transcript when a stream this viewer is not rendering completes', async () => {
+    const { queryClient, fetchTranscript, unsubscribe } = mountDetail({
+      ...liveStream,
+      messages: [{ id: 'stream-1' }] as MothershipChatHistory['messages'],
+    })
+
+    handleMothershipChatStatusEvent(queryClient, 'ws-1', {
+      chatId: 'chat-1',
+      type: 'completed',
+      streamId: 'stream-1',
+    })
+    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)
 }
@@ -65,15 +59,22 @@ function hasNewerKnownActiveStream(current: MothershipChatHistory | undefined, s
   return activeIndex > eventStreamIndex
 }
 
+/**
+ * Returns true when refetching the chat detail for a stream event would only
+ * reload the transcript this client already holds or is about to reload. A
+ * completion of the viewer's own live stream is skipped because the server
+ * persists the turn before closing that stream, and the client's own
+ * finalization refetches the detail once it sees the close.
+ */
 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
-  if (current.activeStreamId === payload.streamId) return false
+  if (current.activeStreamId === payload.streamId) {
+    return payload.type === 'started' || isLocalOptimisticActiveStream(current)
+  }
   if (hasNewerKnownActiveStream(current, payload.streamId)) return true
   return (
     payload.type === 'completed' &&
@@ -128,17 +129,23 @@ 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
+  queryClient.invalidateQueries({ queryKey: mothershipChatKeys.detail(payload.chatId) })
 }
 
 /**