fix(desktop): open remote file rows in the in-app preview

A plain click on a composer file row in remote mode handed the backend's
file:// URL to the local browser bridge, which cannot resolve a path that
only exists on the gateway host. Route remote non-HTML file targets to the
gateway-backed in-app preview pane instead; local files, ordinary URLs, and
remote HTML (staged locally by openPreviewTargetInBrowser) keep their
existing browser path.

Supersedes #70296 and #57878.

Co-authored-by: lesterlxt <153183032+lesterlxt@users.noreply.github.com>
Co-authored-by: cj52973 <cjenkins@scacpa.org>

apps/desktop/src/app/chat/composer/status-stack/preview-row.test.tsx

@@ -1,11 +1,22 @@
-import { cleanup, fireEvent, render, screen } from '@testing-library/react'
-import { afterEach, describe, expect, it } from 'vitest'
+import { cleanup, fireEvent, render, screen, waitFor } from '@testing-library/react'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+import { $previewTabs, closeRightRail } from '@/store/preview'
+import { $connection } from '@/store/session'
 
 import { PreviewStatusRow } from './preview-row'
 
 describe('PreviewStatusRow', () => {
+  beforeEach(() => {
+    $connection.set(null)
+    closeRightRail()
+  })
+
   afterEach(() => {
     cleanup()
+    $connection.set(null)
+    closeRightRail()
+    vi.restoreAllMocks()
   })
 
   it('keeps the preview tooltip label inline inside the portaled decoration', async () => {
@@ -27,4 +38,118 @@ describe('PreviewStatusRow', () => {
     expect(label?.classList.contains('inline-flex')).toBe(true)
     expect(label?.classList.contains('flex')).toBe(false)
   })
+
+  it('opens remote non-HTML file artifacts in the in-app preview instead of the local browser bridge', async () => {
+    const remotePath = '/home/agent/report.pdf'
+    const openPreviewInBrowser = vi.fn(async () => undefined)
+
+    $connection.set({ mode: 'remote' } as never)
+    Object.defineProperty(window, 'hermesDesktop', {
+      configurable: true,
+      value: {
+        api: vi.fn(async () => ({ binary: true, byteSize: 42, mimeType: 'application/pdf' })),
+        normalizePreviewTarget: vi.fn(async () => ({
+          kind: 'file',
+          label: 'report.pdf',
+          path: remotePath,
+          previewKind: 'binary',
+          source: remotePath,
+          url: 'file:///home/agent/report.pdf'
+        })),
+        openPreviewInBrowser
+      }
+    })
+
+    render(
+      <PreviewStatusRow
+        item={{ cwd: '/home/agent', id: remotePath, label: 'report.pdf', target: remotePath }}
+        onDismiss={() => undefined}
+      />
+    )
+
+    fireEvent.click(screen.getByText('report.pdf'))
+
+    await waitFor(() => {
+      expect($previewTabs.get()).toEqual([
+        expect.objectContaining({ target: expect.objectContaining({ kind: 'file', path: remotePath }) })
+      ])
+    })
+    expect(openPreviewInBrowser).not.toHaveBeenCalled()
+  })
+
+  it('keeps local file artifacts on the browser bridge', async () => {
+    const localPath = '/Users/alice/report.pdf'
+    const openPreviewInBrowser = vi.fn(async () => undefined)
+
+    $connection.set({ mode: 'local' } as never)
+    Object.defineProperty(window, 'hermesDesktop', {
+      configurable: true,
+      value: {
+        normalizePreviewTarget: vi.fn(async () => ({
+          kind: 'file',
+          label: 'report.pdf',
+          path: localPath,
+          previewKind: 'binary',
+          source: localPath,
+          url: 'file:///Users/alice/report.pdf'
+        })),
+        openPreviewInBrowser
+      }
+    })
+
+    render(
+      <PreviewStatusRow
+        item={{ cwd: '/Users/alice', id: localPath, label: 'report.pdf', target: localPath }}
+        onDismiss={() => undefined}
+      />
+    )
+
+    fireEvent.click(screen.getByText('report.pdf'))
+
+    await waitFor(() => {
+      expect(openPreviewInBrowser).toHaveBeenCalledWith('file:///Users/alice/report.pdf')
+    })
+    expect($previewTabs.get()).toEqual([])
+  })
+
+  it('keeps remote HTML on the staged browser-open path, not the in-app pane', async () => {
+    const remotePath = '/home/agent/index.html'
+    const html = '<!doctype html><html><body>hi</body></html>'
+    const dataUrl = `data:text/html;base64,${btoa(html)}`
+    const openPreviewInBrowser = vi.fn(async () => undefined)
+    const saveImageBuffer = vi.fn(async () => '/tmp/staged.html')
+
+    $connection.set({ mode: 'remote' } as never)
+    Object.defineProperty(window, 'hermesDesktop', {
+      configurable: true,
+      value: {
+        api: vi.fn(async () => dataUrl),
+        normalizePreviewTarget: vi.fn(async () => ({
+          kind: 'file',
+          label: 'index.html',
+          path: remotePath,
+          previewKind: 'html',
+          source: remotePath,
+          url: 'file:///home/agent/index.html'
+        })),
+        openPreviewInBrowser,
+        saveImageBuffer
+      }
+    })
+
+    render(
+      <PreviewStatusRow
+        item={{ cwd: '/home/agent', id: remotePath, label: 'index.html', target: remotePath }}
+        onDismiss={() => undefined}
+      />
+    )
+
+    fireEvent.click(screen.getByText('index.html'))
+
+    await waitFor(() => {
+      expect(saveImageBuffer).toHaveBeenCalled()
+      expect(openPreviewInBrowser).toHaveBeenCalledWith('file:///tmp/staged.html')
+    })
+    expect($previewTabs.get()).toEqual([])
+  })
 })

apps/desktop/src/app/chat/composer/status-stack/preview-row.tsx

@@ -6,6 +6,7 @@ import { Button } from '@/components/ui/button'
 import { Codicon } from '@/components/ui/codicon'
 import { Tip } from '@/components/ui/tooltip'
 import { useI18n } from '@/i18n'
+import { isDesktopFsRemoteMode } from '@/lib/desktop-fs'
 import { normalizeOrLocalPreviewTarget, openPreviewTargetInBrowser } from '@/lib/local-preview'
 import { cn } from '@/lib/utils'
 import { PREVIEW_PANE_ID } from '@/store/layout'
@@ -59,9 +60,23 @@ export const PreviewStatusRow = memo(function PreviewStatusRow({ item, onDismiss
     }
   }
 
-  const openInBrowser = async () => {
+  const openDefaultTarget = async () => {
     try {
-      await openPreviewTargetInBrowser(await resolveTarget())
+      const target = await resolveTarget()
+
+      // A file:// URL resolved in remote mode names a file on the backend
+      // host, not on the machine running Electron. Keep local files and
+      // ordinary URLs on the browser path, but route remote files through the
+      // in-app preview pane so its filesystem adapter reads via the gateway.
+      // (Remote HTML stays on openPreviewTargetInBrowser, which stages a
+      // sanitized local copy before opening it.)
+      if (target.kind === 'file' && target.previewKind !== 'html' && isDesktopFsRemoteMode()) {
+        openPreview(target, 'tool-result')
+
+        return
+      }
+
+      await openPreviewTargetInBrowser(target)
     } catch (error) {
       notifyError(error, t.preview.unavailable)
     }
@@ -77,13 +92,14 @@ export const PreviewStatusRow = memo(function PreviewStatusRow({ item, onDismiss
           size="0.8rem"
         />
       }
-      // Plain click opens the link in the browser; ⌘/Ctrl-click opens it in the
-      // in-app preview pane instead. (isOpen still toggles the pane closed.)
+      // Plain click opens the link in the browser, except remote files which
+      // only the in-app gateway-backed preview can read. ⌘/Ctrl-click always
+      // uses the in-app preview pane. (isOpen still toggles the pane closed.)
       onActivate={event => {
         if (event.metaKey || event.ctrlKey) {
           void togglePreview()
         } else {
-          void openInBrowser()
+          void openDefaultTarget()
         }
       }}
       trailing={