improvement(chat): speed up conversation navigation

.claude/rules/sim-react-performance.md

@@ -90,6 +90,19 @@ const [{ id }, { kbName }] = await Promise.all([params, searchParams])
 
 Only keep awaits sequential when a later call genuinely uses an earlier result, or when the ordering is deliberate (rate-limited batches, retry loops, write-then-read).
 
+## Prefetch dynamic destination lists on intent
+
+For long lists of dynamic destinations, do not viewport-prefetch every row and do not assume
+`router.prefetch()` warms the full route: in Next 16 it uses the automatic/PPR strategy. Gate
+`<Link prefetch={true}>` behind deliberate hover or keyboard focus, and prefetch destination
+server state with the consumer's shared React Query options. A short, cancelable hover dwell
+avoids drive-by downloads. Do not treat `touchstart` as intent because it also begins scrolling;
+let the actual unmodified click start the data request.
+
+If a continuity-focused surface intentionally omits `loading.tsx` so the current view remains
+mounted until its peer is ready, the intent path must warm both the full route and its critical
+data. Otherwise keep the loading boundary so dynamic navigation remains responsive.
+
 ## Local feature barrels are the convention — do not "fix" them
 
 Tooling (e.g. react-doctor's `no-barrel-import`) will flag imports from local `index.ts` barrels as a bundle cost. In this repo that is a **false positive**: barrel imports for 3+ export folders are mandated by `.claude/rules/sim-imports.md`. Leave them.

.claude/rules/sim-url-state.md

@@ -143,6 +143,11 @@ import KnowledgeBaseLoading from '@/app/workspace/[workspaceId]/knowledge/[id]/l
 
 Reference: `apps/sim/app/workspace/[workspaceId]/knowledge/[id]/page.tsx`.
 
+The narrow exception is a continuity-focused peer switch that deliberately keeps the current
+view mounted and follows the full-route plus critical-data intent-prefetch rule in
+`sim-react-performance.md`. It still needs a real in-page Suspense fallback; it only omits the
+route-level `loading.tsx` that would replace the current peer before the destination is ready.
+
 This applies to **page entries**. An inner `<Suspense>` wrapping a `lazy()` component is the exception: there `fallback={null}` is correct, precisely so the suspend resolves at the nearest boundary instead of flashing the whole route — see `sim-imports.md`, "Code-splitting through barrels".
 
 ## Debounced text inputs

apps/sim/app/workspace/[workspaceId]/home/home.tsx

@@ -38,10 +38,7 @@ import { RESOURCE_HEADER_CLASSES } from '@/app/workspace/[workspaceId]/home/comp
 import { resolveWorkspaceResourceRef } from '@/app/workspace/[workspaceId]/home/resolve-resource-ref'
 import { resourceParam, resourceUrlKeys } from '@/app/workspace/[workspaceId]/home/search-params'
 import { useFolders } from '@/hooks/queries/folders'
-import {
-  useMarkMothershipChatRead,
-  useMothershipChatHistory,
-} from '@/hooks/queries/mothership-chats'
+import { useMarkMothershipChatRead } from '@/hooks/queries/mothership-chats'
 import { useWorkflows } from '@/hooks/queries/workflows'
 import { getWorkspaceFilesQueryOptions, useWorkspaceFiles } from '@/hooks/queries/workspace-files'
 import { useOAuthReturnRouter } from '@/hooks/use-oauth-return'
@@ -205,7 +202,6 @@ export function Home({ chatId, userName, userId, tableViewsEnabled }: HomeProps)
 
   const wasSendingRef = useRef(false)
 
-  const { isPending: isChatHistoryPending } = useMothershipChatHistory(chatId)
   const { mutate: markRead } = useMarkMothershipChatRead(workspaceId)
 
   const [isResourceCollapsed, setIsResourceCollapsed] = useState(true)
@@ -242,6 +238,7 @@ export function Home({ chatId, userName, userId, tableViewsEnabled }: HomeProps)
 
   const {
     messages,
+    isChatHistoryPending,
     isSending,
     isReconnecting,
     sendMessage,

apps/sim/app/workspace/[workspaceId]/home/hooks/use-chat.ts

@@ -193,6 +193,7 @@ interface WithdrawnSend {
 
 export interface UseChatReturn {
   messages: ChatMessage[]
+  isChatHistoryPending: boolean
   isSending: boolean
   isReconnecting: boolean
   error: string | null
@@ -1790,7 +1791,8 @@ export function useChat(
     [flushPendingResources, queryClient, workspaceId]
   )
 
-  const { data: chatHistory } = useMothershipChatHistory(resolvedChatId)
+  const { data: chatHistory, isPending: isChatHistoryPending } =
+    useMothershipChatHistory(resolvedChatId)
   const messages = useMemo(() => {
     const source = chatHistory?.messages.map(toDisplayMessage) ?? pendingMessages
     return source.map((m) => restoreRevealedSimKeysForMessage(m, revealedSimKeysRef.current))
@@ -5210,6 +5212,7 @@ export function useChat(
 
   return {
     messages,
+    isChatHistoryPending,
     isSending,
     isReconnecting,
     error,

apps/sim/app/workspace/[workspaceId]/w/components/sidebar/components/chat-navigation-link/chat-navigation-link.test.tsx

@@ -0,0 +1,293 @@
+/**
+ * @vitest-environment jsdom
+ */
+import { act } from 'react'
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
+import { createRoot, type Root } from 'react-dom/client'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+const { linkPrefetch } = vi.hoisted(() => ({
+  linkPrefetch: vi.fn(),
+}))
+
+vi.mock('next/link', () => ({
+  default: ({
+    href,
+    children,
+    prefetch,
+    ...props
+  }: {
+    href: string
+    children: React.ReactNode
+    prefetch?: boolean
+  }) => {
+    linkPrefetch(prefetch)
+    return (
+      <a href={href} {...props}>
+        {children}
+      </a>
+    )
+  },
+}))
+
+import { ChatNavigationLink } from '@/app/workspace/[workspaceId]/w/components/sidebar/components/chat-navigation-link/chat-navigation-link'
+
+describe('ChatNavigationLink', () => {
+  let container: HTMLDivElement
+  let queryClient: QueryClient
+  let root: Root
+  let prefetchQuery: ReturnType<typeof vi.spyOn>
+
+  beforeEach(() => {
+    ;(globalThis as { IS_REACT_ACT_ENVIRONMENT?: boolean }).IS_REACT_ACT_ENVIRONMENT = true
+    vi.useFakeTimers()
+    linkPrefetch.mockReset()
+    queryClient = new QueryClient({ defaultOptions: { queries: { retry: false } } })
+    prefetchQuery = vi.spyOn(queryClient, 'prefetchQuery').mockResolvedValue()
+    container = document.createElement('div')
+    document.body.appendChild(container)
+    root = createRoot(container)
+  })
+
+  afterEach(() => {
+    act(() => root.unmount())
+    container.remove()
+    queryClient.clear()
+    vi.useRealTimers()
+  })
+
+  function renderLink(chatId = 'chat-1', isCurrentRoute = false) {
+    act(() => {
+      root.render(
+        <QueryClientProvider client={queryClient}>
+          <ChatNavigationLink
+            chatId={chatId}
+            href={`/workspace/ws-1/chat/${chatId}`}
+            isCurrentRoute={isCurrentRoute}
+          >
+            Open chat
+          </ChatNavigationLink>
+        </QueryClientProvider>
+      )
+    })
+    const link = container.querySelector('a')
+    if (!link) throw new Error('chat link not rendered')
+    return link
+  }
+
+  function pointerEvent(type: string, pointerType: 'mouse' | 'touch', init?: MouseEventInit) {
+    const event = new MouseEvent(type, { bubbles: true, ...init })
+    Object.defineProperty(event, 'pointerType', { value: pointerType })
+    return event
+  }
+
+  it('prefetches the route and exact history after deliberate pointer intent', () => {
+    const link = renderLink()
+
+    act(() => {
+      link.dispatchEvent(new MouseEvent('mouseover', { bubbles: true }))
+      vi.advanceTimersByTime(79)
+    })
+    expect(linkPrefetch).toHaveBeenLastCalledWith(false)
+    expect(prefetchQuery).not.toHaveBeenCalled()
+
+    act(() => vi.advanceTimersByTime(1))
+
+    expect(linkPrefetch).toHaveBeenLastCalledWith(true)
+    expect(prefetchQuery).toHaveBeenCalledWith(
+      expect.objectContaining({
+        queryKey: ['mothership-chats', 'detail', 'chat-1'],
+        staleTime: 30_000,
+      })
+    )
+
+    act(() => link.dispatchEvent(new MouseEvent('mouseout', { bubbles: true })))
+
+    expect(linkPrefetch).toHaveBeenLastCalledWith(false)
+    expect(prefetchQuery).toHaveBeenCalledTimes(1)
+  })
+
+  it('cancels drive-by hover prefetches', () => {
+    const link = renderLink()
+
+    act(() => {
+      link.dispatchEvent(new MouseEvent('mouseover', { bubbles: true }))
+      link.dispatchEvent(new MouseEvent('mouseout', { bubbles: true }))
+      vi.runAllTimers()
+    })
+
+    expect(linkPrefetch).toHaveBeenLastCalledWith(false)
+    expect(prefetchQuery).not.toHaveBeenCalled()
+  })
+
+  it('prefetches immediately for keyboard focus without fetching a new-chat history', () => {
+    const link = renderLink('new')
+
+    act(() => link.dispatchEvent(new FocusEvent('focusin', { bubbles: true })))
+
+    expect(linkPrefetch).toHaveBeenLastCalledWith(true)
+    expect(prefetchQuery).not.toHaveBeenCalled()
+  })
+
+  it('does not treat touch scrolling as navigation intent', () => {
+    const link = renderLink()
+
+    act(() => link.dispatchEvent(new TouchEvent('touchstart', { bubbles: true })))
+
+    expect(linkPrefetch).toHaveBeenLastCalledWith(false)
+    expect(prefetchQuery).not.toHaveBeenCalled()
+  })
+
+  it('prefetches before direct mouse clicks and completed touch taps', () => {
+    const link = renderLink()
+    linkPrefetch.mockClear()
+
+    act(() => {
+      link.dispatchEvent(pointerEvent('pointerdown', 'mouse', { button: 0 }))
+      link.dispatchEvent(new MouseEvent('click', { bubbles: true, cancelable: true }))
+    })
+
+    expect(linkPrefetch).toHaveBeenLastCalledWith(true)
+    expect(prefetchQuery).toHaveBeenCalledTimes(1)
+
+    act(() => link.dispatchEvent(new FocusEvent('focusout', { bubbles: true })))
+    linkPrefetch.mockClear()
+    prefetchQuery.mockClear()
+    act(() => {
+      link.dispatchEvent(pointerEvent('pointerup', 'touch', { button: 0 }))
+      link.dispatchEvent(new MouseEvent('click', { bubbles: true, cancelable: true }))
+    })
+
+    expect(linkPrefetch).toHaveBeenLastCalledWith(true)
+    expect(prefetchQuery).toHaveBeenCalledTimes(1)
+  })
+
+  it('cancels touch-scroll pointer intent before it can prefetch', () => {
+    const link = renderLink()
+
+    act(() => {
+      link.dispatchEvent(pointerEvent('pointerdown', 'touch', { button: 0 }))
+      link.dispatchEvent(pointerEvent('pointercancel', 'touch', { button: 0 }))
+    })
+
+    expect(linkPrefetch).toHaveBeenLastCalledWith(false)
+    expect(prefetchQuery).not.toHaveBeenCalled()
+  })
+
+  it('does not prefetch when a nested chat action is pressed', () => {
+    act(() => {
+      root.render(
+        <QueryClientProvider client={queryClient}>
+          <ChatNavigationLink chatId='chat-1' href='/workspace/ws-1/chat/chat-1'>
+            <button type='button' onClick={(event) => event.preventDefault()}>
+              Chat options
+            </button>
+          </ChatNavigationLink>
+        </QueryClientProvider>
+      )
+    })
+    const button = container.querySelector('button')
+    if (!button) throw new Error('chat action not rendered')
+
+    act(() => {
+      button.dispatchEvent(pointerEvent('pointerdown', 'mouse', { button: 0 }))
+      button.dispatchEvent(pointerEvent('pointerup', 'touch', { button: 0 }))
+      button.dispatchEvent(new MouseEvent('click', { bubbles: true, cancelable: true }))
+    })
+
+    expect(linkPrefetch).toHaveBeenLastCalledWith(false)
+    expect(prefetchQuery).not.toHaveBeenCalled()
+  })
+
+  it('does not prefetch the chat that is already open', () => {
+    const link = renderLink('chat-1', true)
+
+    act(() => link.dispatchEvent(new FocusEvent('focusin', { bubbles: true })))
+
+    expect(linkPrefetch).toHaveBeenLastCalledWith(false)
+    expect(prefetchQuery).not.toHaveBeenCalled()
+  })
+
+  it('clears prior intent when a persistent row changes route roles', () => {
+    const renderRouteRole = (isCurrentRoute: boolean) => {
+      act(() => {
+        root.render(
+          <QueryClientProvider client={queryClient}>
+            <ChatNavigationLink
+              chatId='chat-1'
+              href='/workspace/ws-1/chat/chat-1'
+              isCurrentRoute={isCurrentRoute}
+            >
+              Open chat
+            </ChatNavigationLink>
+          </QueryClientProvider>
+        )
+      })
+    }
+
+    renderRouteRole(false)
+    const link = container.querySelector('a')
+    if (!link) throw new Error('chat link not rendered')
+    act(() => {
+      link.dispatchEvent(pointerEvent('pointerdown', 'mouse', { button: 0 }))
+      link.dispatchEvent(new MouseEvent('click', { bubbles: true, cancelable: true }))
+    })
+    expect(linkPrefetch).toHaveBeenLastCalledWith(true)
+
+    renderRouteRole(true)
+    renderRouteRole(false)
+
+    expect(linkPrefetch).toHaveBeenLastCalledWith(false)
+    prefetchQuery.mockClear()
+    const destinationLink = container.querySelector('a')
+    if (!destinationLink) throw new Error('destination link not rendered')
+    act(() => {
+      destinationLink.dispatchEvent(new MouseEvent('click', { bubbles: true, cancelable: true }))
+    })
+    expect(prefetchQuery).toHaveBeenCalledTimes(1)
+  })
+
+  it('does not prefetch when the click is canceled or opens another browsing context', () => {
+    const canceledLink = renderLink()
+
+    act(() => {
+      root.render(
+        <QueryClientProvider client={queryClient}>
+          <ChatNavigationLink
+            chatId='chat-1'
+            href='/workspace/ws-1/chat/chat-1'
+            onClick={(event) => event.preventDefault()}
+          >
+            Open chat
+          </ChatNavigationLink>
+        </QueryClientProvider>
+      )
+    })
+    act(() => {
+      canceledLink.dispatchEvent(new MouseEvent('click', { bubbles: true, cancelable: true }))
+    })
+
+    expect(linkPrefetch).toHaveBeenLastCalledWith(false)
+    expect(prefetchQuery).not.toHaveBeenCalled()
+
+    act(() => {
+      root.render(
+        <QueryClientProvider client={queryClient}>
+          <ChatNavigationLink chatId='chat-1' href='/workspace/ws-1/chat/chat-1'>
+            Open chat
+          </ChatNavigationLink>
+        </QueryClientProvider>
+      )
+    })
+    const modifiedLink = container.querySelector('a')
+    if (!modifiedLink) throw new Error('chat link not rendered')
+    act(() => {
+      modifiedLink.dispatchEvent(
+        new MouseEvent('click', { bubbles: true, cancelable: true, metaKey: true })
+      )
+    })
+
+    expect(linkPrefetch).toHaveBeenLastCalledWith(false)
+    expect(prefetchQuery).not.toHaveBeenCalled()
+  })
+})