fix(desktop): ⌘W closes visible file tab when preview selection is stale (#68639)

* fix(desktop): make ⌘W close visible file tab on stale preview selection

When the live preview target is gone but $rightRailActiveTabId still points
at preview, file tabs remain on screen while ⌘W fell through to a workspace
no-op. Close the visible file tab instead.

* test(desktop): cover ⌘W close for file tabs and ghost preview selection

Lock the happy path and the stale-preview regression so ⌘W keeps closing
the file tab the rail is actually showing.

apps/desktop/src/app/chat/close-tab.test.ts

@@ -0,0 +1,65 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+import { $rightRailActiveTabId, RIGHT_RAIL_PREVIEW_TAB_ID } from '@/store/layout'
+import {
+  $filePreviewTabs,
+  $previewTarget,
+  clearSessionPreviewRegistry,
+  type PreviewTarget,
+  setCurrentSessionPreviewTarget
+} from '@/store/preview'
+import { $activeSessionId, $selectedStoredSessionId } from '@/store/session'
+
+import { closeActiveTab } from './close-tab'
+
+function fileTarget(path: string): PreviewTarget {
+  return {
+    kind: 'file',
+    label: path,
+    path,
+    previewKind: 'text',
+    source: path,
+    url: `file://${path}`
+  }
+}
+
+describe('closeActiveTab', () => {
+  beforeEach(() => {
+    vi.stubGlobal('document', { activeElement: null })
+    $activeSessionId.set('session-1')
+    $selectedStoredSessionId.set(null)
+    window.localStorage.clear()
+    clearSessionPreviewRegistry()
+  })
+
+  afterEach(() => {
+    vi.unstubAllGlobals()
+    $activeSessionId.set(null)
+    $selectedStoredSessionId.set(null)
+    clearSessionPreviewRegistry()
+    window.localStorage.clear()
+  })
+
+  it('closes the active file preview tab (⌘W happy path)', () => {
+    setCurrentSessionPreviewTarget(fileTarget('/work/notes.md'), 'manual')
+
+    expect($filePreviewTabs.get()).toHaveLength(1)
+    expect($rightRailActiveTabId.get()).toBe('file:file:///work/notes.md')
+
+    expect(closeActiveTab()).toBe(true)
+    expect($filePreviewTabs.get()).toHaveLength(0)
+  })
+
+  it('closes the visible file tab when active selection is a ghost preview', () => {
+    // Active tab id stuck on live-preview after that target was cleared, while
+    // file tabs remain (UI falls back to tabs[0] until React syncs). ⌘W must
+    // close the visible file tab instead of no-op'ing via closeWorkspaceTab().
+    setCurrentSessionPreviewTarget(fileTarget('/work/notes.md'), 'manual')
+    $previewTarget.set(null)
+    $rightRailActiveTabId.set(RIGHT_RAIL_PREVIEW_TAB_ID)
+
+    expect($filePreviewTabs.get()).toHaveLength(1)
+    expect(closeActiveTab()).toBe(true)
+    expect($filePreviewTabs.get()).toHaveLength(0)
+  })
+})

apps/desktop/src/app/chat/close-tab.ts

@@ -1,12 +1,12 @@
 import { closeActiveTerminal } from '@/app/right-sidebar/terminal/terminals'
 import { closeWorkspaceTab } from '@/components/pane-shell/tree/store'
 import { isFocusWithin } from '@/lib/keybinds/combo'
-import { $filePreviewTarget, $previewTarget, closeActiveRightRailTab } from '@/store/preview'
+import { $filePreviewTabs, $previewTarget, closeActiveRightRailTab } from '@/store/preview'
 
 /**
  * ⌘W — close the tab of the context you're in, by precedence:
  *   1. a focused terminal → its active terminal tab,
- *   2. an open preview → its active preview tab (unchanged from pre-tiling),
+ *   2. right-rail tabs (live preview and/or file peeks),
  *   3. the MAIN zone → its active tab (a session tile stacked into the workspace).
  * Returns false when nothing closes, so ⌘W is a no-op — it never closes the
  * window (a bare workspace stays put). Shared by the keyboard path (Win/Linux)
@@ -19,10 +19,13 @@ export function closeActiveTab(): boolean {
     return true
   }
 
-  if ($filePreviewTarget.get() || $previewTarget.get()) {
-    closeActiveRightRailTab()
-
-    return true
+  // Prefer tab *presence* over the derived active file target. After the live
+  // preview is cleared, `$rightRailActiveTabId` can stay on `preview` while
+  // file tabs remain (the rail UI falls back to tabs[0]). Gating only on
+  // `$filePreviewTarget` made ⌘W fall through to closeWorkspaceTab() and look
+  // broken with a file tab still on screen.
+  if ($previewTarget.get() || $filePreviewTabs.get().length > 0) {
+    return closeActiveRightRailTab()
   }
 
   return closeWorkspaceTab()

apps/desktop/src/store/preview.ts

@@ -87,6 +87,16 @@ if (
   selectRightRailTab(RIGHT_RAIL_PREVIEW_TAB_ID)
 }
 
+// Inverse: persisted/default active id is still the live-preview tab, but that
+// target isn't open and file tabs are. Point at the first file tab so ⌘W and
+// the strip agree before React's fallback sync runs.
+if (
+  $rightRailActiveTabId.get() === RIGHT_RAIL_PREVIEW_TAB_ID &&
+  $filePreviewTabs.get().length > 0
+) {
+  selectRightRailTab($filePreviewTabs.get()[0]!.id)
+}
+
 export const $filePreviewTarget = computed([$filePreviewTabs, $rightRailActiveTabId], (tabs, activeTabId) => {
   if (!activeTabId.startsWith('file:')) {
     return null
@@ -460,7 +470,40 @@ export function closeRightRailTab(tabId: RightRailTabId) {
   closeFilePreviewTab(tabId)
 }
 
-export const closeActiveRightRailTab = () => closeRightRailTab($rightRailActiveTabId.get())
+/** Close the tab the right rail is actually showing. Returns false when nothing
+ *  closed (so ⌘W can fall through). Resolves a stale `preview` selection to the
+ *  first file tab when the live preview target is already gone. */
+export function closeActiveRightRailTab(): boolean {
+  let tabId = $rightRailActiveTabId.get()
+
+  if (tabId === RIGHT_RAIL_PREVIEW_TAB_ID && !$previewTarget.get()) {
+    const fallback = $filePreviewTabs.get()[0]?.id
+
+    if (!fallback) {
+      return false
+    }
+
+    tabId = fallback
+  }
+
+  if (tabId === RIGHT_RAIL_PREVIEW_TAB_ID) {
+    if (!$previewTarget.get()) {
+      return false
+    }
+
+    closeRightRailTab(tabId)
+
+    return true
+  }
+
+  if (!$filePreviewTabs.get().some(tab => tab.id === tabId)) {
+    return false
+  }
+
+  closeRightRailTab(tabId)
+
+  return true
+}
 
 // The rail's visible tab order: the live preview tab (when present) first, then
 // the file tabs in their stored order. Mirrors `ChatPreviewRail`'s `tabs` memo