fix(desktop): isolate preview artifact chips per session view

apps/desktop/src/components/assistant-ui/tool/fallback-preview-isolation.test.tsx

@@ -0,0 +1,112 @@
+import type { ToolCallMessagePartProps } from '@assistant-ui/react'
+import { cleanup, render, waitFor } from '@testing-library/react'
+import { atom } from 'nanostores'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+import { type SessionView, SessionViewProvider } from '@/app/chat/session-view'
+import { I18nProvider } from '@/i18n'
+import { $previewStatusBySession } from '@/store/preview-status'
+import { $activeSessionId, $currentCwd } from '@/store/session'
+
+import { ToolFallback } from './fallback'
+
+vi.mock('@assistant-ui/react', async importOriginal => {
+  const actual = await importOriginal<Record<string, unknown>>()
+
+  return {
+    ...actual,
+    useAuiState: vi.fn((selector: (state: unknown) => unknown) =>
+      selector({
+        message: {
+          id: 'assistant-b',
+          status: { type: 'complete', reason: 'stop' }
+        },
+        thread: { isRunning: false }
+      })
+    )
+  }
+})
+
+Element.prototype.animate = function animate() {
+  return {
+    cancel: () => {},
+    finished: Promise.resolve()
+  } as unknown as Animation
+}
+
+function tileView(runtimeId: string, cwd: string): SessionView {
+  return {
+    kind: 'tile',
+    $awaitingResponse: atom(false),
+    $busy: atom(false),
+    $cwd: atom(cwd),
+    $fast: atom(false),
+    $lastVisibleIsUser: atom(false),
+    $messages: atom([]),
+    $messagesEmpty: atom(true),
+    $model: atom(''),
+    $provider: atom(''),
+    $reasoningEffort: atom(''),
+    $runtimeId: atom(runtimeId),
+    $storedId: atom(`stored-${runtimeId}`)
+  }
+}
+
+function previewToolProps(): ToolCallMessagePartProps {
+  return {
+    addResult: vi.fn(),
+    args: { path: '/work/b/creator.html' },
+    argsText: JSON.stringify({ path: '/work/b/creator.html' }),
+    isError: false,
+    respondToApproval: vi.fn(),
+    result: { ok: true },
+    resume: vi.fn(),
+    status: { type: 'complete' },
+    toolCallId: 'preview-b-1',
+    toolName: 'search_files',
+    type: 'tool-call'
+  }
+}
+
+beforeEach(() => {
+  $previewStatusBySession.set({})
+  $activeSessionId.set('session-a')
+  $currentCwd.set('/work/a')
+})
+
+afterEach(() => {
+  cleanup()
+  $previewStatusBySession.set({})
+  $activeSessionId.set(null)
+  $currentCwd.set('')
+})
+
+describe('ToolFallback preview session isolation (#66411)', () => {
+  it('records preview artifacts under the owning session view, not the global active session', async () => {
+    const sessionB = tileView('session-b', '/work/b')
+
+    render(
+      <I18nProvider configClient={null} initialLocale="en">
+        <SessionViewProvider value={sessionB}>
+          <ToolFallback {...previewToolProps()} />
+        </SessionViewProvider>
+      </I18nProvider>
+    )
+
+    await waitFor(() => {
+      expect($previewStatusBySession.get()['session-b']?.map(item => item.id)).toEqual(['/work/b/creator.html'])
+    })
+
+    expect($previewStatusBySession.get()['session-a']).toBeUndefined()
+
+    // Global focus flips to A while B's mounted tool row stays mounted — must
+    // not re-key the artifact into A's bucket.
+    $activeSessionId.set('session-a')
+    $currentCwd.set('/work/a')
+
+    await waitFor(() => {
+      expect($previewStatusBySession.get()['session-b']?.map(item => item.id)).toEqual(['/work/b/creator.html'])
+    })
+    expect($previewStatusBySession.get()['session-a']).toBeUndefined()
+  })
+})

apps/desktop/src/components/assistant-ui/tool/fallback.tsx

@@ -16,6 +16,7 @@ import {
   useState
 } from 'react'
 
+import { useSessionView } from '@/app/chat/session-view'
 import { AnsiText } from '@/components/assistant-ui/ansi-text'
 import { useElapsedSeconds } from '@/components/chat/activity-timer'
 import { ActivityTimerText } from '@/components/chat/activity-timer-text'
@@ -38,7 +39,6 @@ import { normalize } from '@/lib/text'
 import { useEnterAnimation } from '@/lib/use-enter-animation'
 import { cn } from '@/lib/utils'
 import { recordPreviewArtifact } from '@/store/preview-status'
-import { $activeSessionId, $currentCwd } from '@/store/session'
 import { $toolInlineDiff } from '@/store/tool-diffs'
 import { $toolRowDismissed, dismissToolRow } from '@/store/tool-dismiss'
 import { $toolDisclosureOpen, $toolViewMode, setToolDisclosureOpen } from '@/store/tool-view'
@@ -309,25 +309,22 @@ function ToolEntry({ part }: ToolEntryProps) {
   }, [inlineDiff, isPending, result, stablePart])
 
   // Surface a previewable artifact (HTML file / localhost URL) as a compact link
-  // in the composer status stack rather than a bulky inline card. Uses the same
-  // detected target the old inline card did, keyed to the active session the
-  // stack reads from. Idempotent + dedup'd, so re-renders don't churn.
+  // in the composer status stack rather than a bulky inline card. Keyed to the
+  // owning session view (primary or tile), not the global active session — in
+  // multi-session split both panes stay mounted and focus can flip freely.
+  // Idempotent + dedup'd, so re-renders don't churn.
+  const sessionView = useSessionView()
+  const owningSessionId = useStore(sessionView.$runtimeId)
+  const owningCwd = useStore(sessionView.$cwd)
   const previewTarget = view.previewTarget
 
   useEffect(() => {
-    if (isPending || !previewTarget || !isPreviewableTarget(previewTarget)) {
+    if (isPending || !owningSessionId || !previewTarget || !isPreviewableTarget(previewTarget)) {
       return
     }
 
-    // Read (don't subscribe) session/cwd: this only fires when a previewable
-    // target appears, and subscribing re-rendered every tool row on any session
-    // or cwd change.
-    const activeSessionId = $activeSessionId.get()
-
-    if (activeSessionId) {
-      recordPreviewArtifact(activeSessionId, previewTarget, $currentCwd.get() || '')
-    }
-  }, [isPending, previewTarget])
+    recordPreviewArtifact(owningSessionId, previewTarget, owningCwd || '')
+  }, [isPending, owningCwd, owningSessionId, previewTarget])
 
   const detailSections = useMemo(() => {
     if (!view.detail) {