Downloads jump: reuse an open pane instead of duplicating the view

When a pane already shows the downloaded file's folder, the "jump to file" flows now reveal the file there instead of re-opening the same folder in the focused pane (which destroyed that pane's location and duplicated the view). User feedback: with jump-to-download on and Downloads already open in one pane, the other pane opened it again.

- Add `revealFileInBestPane` / `navigateToDirInBestPane` in `navigate-and-select.ts`: pick the target pane in priority order — focused pane already shows the dir (cursor move only), else the other pane shows it (focus shift + cursor move), else navigate the focused pane (unchanged fallback).
- Match is volume-safe and active-tab-only, mirroring `commitPathFromListing`'s drop-foreign-listings policy: a real local volume that contains the path (`isPathOnVolume`), never a `network`/`search-results`/MTP pane reporting a same-looking path string.
- Route all downloads jump entry points through the new helpers: `goToLatestDownload` (⌘J, command palette, MCP), `goToDownload` (toast click + "Jump to file"), the global ⌃⌥⌘J hotkey, and the empty-Downloads toast's "Go to Downloads" action. The empty-toast action still snapshots the Downloads dir at toast-add time but re-evaluates which pane shows it at click time.
- Leave the shared `navigateToFileInPane` / `navigateToDirInPane` primitives unchanged, so "Go to path" (⌘G) keeps its always-navigate behavior.
- Expose `setFocusedPane` and `getPaneLocation` (active-tab volume id + volume path + path) on `ExplorerAPI`, wired through `DualPaneExplorer.svelte`.
- Update the downloads `CLAUDE.md` (pane-reuse note + smoke steps) and navigation `DETAILS.md`.

Author: vdavid

apps/desktop/src/lib/downloads/CLAUDE.md

@@ -108,6 +108,16 @@ the NEXT toast's `initialCollapsed` reflects it. The `ToastItem` host extends th
 The split matters when a burst of downloads arrives: each toast must take the user to the file IT advertised, not to
 whichever file is most recent at click time.
 
+**Pane reuse.** All jump entry points (`goToLatestDownload`, `goToDownload`, and the empty-toast "Go to Downloads"
+action) reveal the target through the `revealFileInBestPane` / `navigateToDirInBestPane` helpers in
+`file-explorer/navigation/navigate-and-select.ts`, NOT the plain `navigateToFileInPane`. If a pane already shows the
+file's `parentDir`, those helpers move the cursor there (focused pane) or shift focus to the other pane — no
+re-navigation, so an already-open Downloads view isn't duplicated. Only when neither pane shows the dir do they navigate
+the focused pane. The match is the pane's ACTIVE tab only and volume-safe (a real local volume that contains the path;
+an MTP or network pane at a same-looking path never counts). The empty-toast action snapshots the Downloads dir at
+toast-add time but re-evaluates which pane shows it at CLICK time. "Go to path" (⌘G) deliberately keeps the
+always-navigate behavior and does NOT reuse panes.
+
 ## FDA defense-in-depth
 
 The watcher won't emit `download-detected` when the FDA gate is closed — that's the contract enforced in
@@ -171,11 +181,15 @@ or the settings rows. Each step is independent; you can stop after the ones that
 2. Wait for the FDA gate to open (existing onboarding). If FDA is already granted in System Settings, the gate clears
    automatically.
 3. Drop a file via Terminal: `touch ~/Downloads/test1.txt` → expect a Downloads toast in Cmdr.
-4. Click the toast body (anywhere outside the buttons) → the focused pane navigates to `~/Downloads` and selects
-   `test1.txt`.
-5. Press `⌘J` from a Cmdr-focused window → the focused pane goes to the latest download (`test1.txt`).
-6. `Cmd-Tab` to Chrome, press `⌃⌥⌘J` → Cmdr foregrounds and goes to `test1.txt`. The first trigger of this session shows
-   the warn toast ("The ⌃⌥⌘J shortcut jumps to your latest download from anywhere. Keep it on?").
+4. With neither pane on `~/Downloads`, click the toast body (anywhere outside the buttons) → the focused pane navigates
+   to `~/Downloads` and selects `test1.txt`.
+5. Pane reuse: open `~/Downloads` in the LEFT pane, focus the RIGHT pane, then press `⌘J` → focus shifts to the left
+   pane and the cursor lands on `test1.txt`; the right pane is untouched (no duplicate Downloads view). Now with the
+   FOCUSED pane already on `~/Downloads`, press `⌘J` again → just the cursor moves, no re-navigation and no focus
+   change.
+6. `Cmd-Tab` to Chrome, press `⌃⌥⌘J` → Cmdr foregrounds and reveals `test1.txt` (reusing a pane already on
+   `~/Downloads`, else navigating the focused pane). The first trigger of this session shows the warn toast ("The ⌃⌥⌘J
+   shortcut jumps to your latest download from anywhere. Keep it on?").
 7. Click "Keep it on" on the warn toast → `acknowledged` flips to `true`; subsequent triggers don't show the toast.
 8. Copy five files via Cmdr into `~/Downloads` (Cmd+C + Cmd+V or drag) → expect NO downloads toasts (Cmdr-own-write
    suppression).

apps/desktop/src/lib/downloads/go-to-latest.test.ts

@@ -12,6 +12,8 @@ const {
   navigateMock,
   moveCursorMock,
   getFocusedPaneMock,
+  getPaneLocationMock,
+  setFocusedPaneMock,
 } = vi.hoisted(() => ({
   goToLatestDownloadMock: vi.fn(),
   downloadsWatcherStatusMock: vi.fn(),
@@ -21,6 +23,14 @@ const {
   navigateMock: vi.fn((): NavigateResult => ({ status: 'started', settled: Promise.resolve() })),
   moveCursorMock: vi.fn(() => Promise.resolve()),
   getFocusedPaneMock: vi.fn(() => 'left'),
+  // Pane active-tab location getter. Default: both panes elsewhere, on the main
+  // local volume, so the pane-reuse check fails and the focused pane navigates.
+  getPaneLocationMock: vi.fn((): { volumeId: string; volumePath: string; path: string } => ({
+    volumeId: 'root',
+    volumePath: '/',
+    path: '/Users/me/elsewhere',
+  })),
+  setFocusedPaneMock: vi.fn(),
 }))
 
 vi.mock('$lib/ipc/bindings', () => ({
@@ -58,16 +68,33 @@ import LatestDownloadFdaToastContent from './LatestDownloadFdaToastContent.svelt
 import type { ExplorerAPI } from '../../routes/(main)/explorer-api'
 
 function makeExplorerStub(): ExplorerAPI {
-  // Only the three methods this helper touches need real stubs. Everything
-  // else is unused; the typed stub avoids a `Partial<ExplorerAPI>` cast leaking
-  // into the helper's call sites.
+  // Only the methods these helpers touch need real stubs. Everything else is
+  // unused; the typed stub avoids a `Partial<ExplorerAPI>` cast leaking into the
+  // helper's call sites.
   return {
     getFocusedPane: getFocusedPaneMock,
     navigate: navigateMock,
     moveCursor: moveCursorMock,
+    getPaneLocation: getPaneLocationMock,
+    setFocusedPane: setFocusedPaneMock,
   } as unknown as ExplorerAPI
 }
 
+/**
+ * Helper: wire `getPaneLocation` so a given pane's active tab shows `path` on a
+ * real local volume (so the pane-reuse match succeeds), while the other pane
+ * sits elsewhere. `volumeId`/`volumePath` default to the main local volume.
+ */
+function paneShows(
+  pane: 'left' | 'right',
+  path: string,
+  volume: { volumeId: string; volumePath: string } = { volumeId: 'root', volumePath: '/' },
+): void {
+  getPaneLocationMock.mockImplementation((p: 'left' | 'right') =>
+    p === pane ? { ...volume, path } : { volumeId: 'root', volumePath: '/', path: '/Users/me/elsewhere' },
+  )
+}
+
 describe('goToLatestDownload', () => {
   beforeEach(() => {
     goToLatestDownloadMock.mockReset()
@@ -77,6 +104,8 @@ describe('goToLatestDownload', () => {
     navigateMock.mockReset().mockReturnValue({ status: 'started', settled: Promise.resolve() })
     moveCursorMock.mockReset().mockResolvedValue(undefined)
     getFocusedPaneMock.mockReset().mockReturnValue('left')
+    getPaneLocationMock.mockReset().mockReturnValue({ volumeId: 'root', volumePath: '/', path: '/Users/me/elsewhere' })
+    setFocusedPaneMock.mockReset()
   })
 
   it('navigates the focused pane and selects the file on success', async () => {
@@ -97,6 +126,93 @@ describe('goToLatestDownload', () => {
     expect(addToastMock).not.toHaveBeenCalled()
   })
 
+  it('moves the cursor only (no navigate, no focus shift) when the focused pane already shows the dir', async () => {
+    goToLatestDownloadMock.mockResolvedValue({
+      status: 'ok',
+      data: { path: '/Users/me/Downloads/report.pdf', parentDir: '/Users/me/Downloads', fileName: 'report.pdf' },
+    })
+    getFocusedPaneMock.mockReturnValue('left')
+    paneShows('left', '/Users/me/Downloads')
+
+    await goToLatestDownload(makeExplorerStub())
+
+    expect(navigateMock).not.toHaveBeenCalled()
+    expect(setFocusedPaneMock).not.toHaveBeenCalled()
+    expect(moveCursorMock).toHaveBeenCalledWith('left', 'report.pdf')
+  })
+
+  it('shifts focus and moves the cursor (no navigate) when the OTHER pane already shows the dir', async () => {
+    goToLatestDownloadMock.mockResolvedValue({
+      status: 'ok',
+      data: { path: '/Users/me/Downloads/report.pdf', parentDir: '/Users/me/Downloads', fileName: 'report.pdf' },
+    })
+    getFocusedPaneMock.mockReturnValue('left')
+    paneShows('right', '/Users/me/Downloads')
+
+    await goToLatestDownload(makeExplorerStub())
+
+    expect(navigateMock).not.toHaveBeenCalled()
+    expect(setFocusedPaneMock).toHaveBeenCalledWith('right')
+    expect(moveCursorMock).toHaveBeenCalledWith('right', 'report.pdf')
+  })
+
+  it('navigates the focused pane when neither pane shows the dir', async () => {
+    goToLatestDownloadMock.mockResolvedValue({
+      status: 'ok',
+      data: { path: '/Users/me/Downloads/report.pdf', parentDir: '/Users/me/Downloads', fileName: 'report.pdf' },
+    })
+    getFocusedPaneMock.mockReturnValue('left')
+    // Both panes sit elsewhere (the beforeEach default).
+
+    await goToLatestDownload(makeExplorerStub())
+
+    expect(navigateMock).toHaveBeenCalledWith({ pane: 'left', to: { path: '/Users/me/Downloads' }, source: 'user' })
+    expect(setFocusedPaneMock).not.toHaveBeenCalled()
+    expect(moveCursorMock).toHaveBeenCalledWith('left', 'report.pdf')
+  })
+
+  it('does NOT count a pane at an equal-looking path on a virtual or device volume as showing the dir', async () => {
+    goToLatestDownloadMock.mockResolvedValue({
+      status: 'ok',
+      data: { path: '/Users/me/Downloads/report.pdf', parentDir: '/Users/me/Downloads', fileName: 'report.pdf' },
+    })
+    getFocusedPaneMock.mockReturnValue('left')
+    // The other pane's active tab reports the exact same path string, but it's on
+    // a network volume (its volumePath is `smb://…`, not a real local mount). It
+    // must not count, so the focused pane navigates as usual.
+    getPaneLocationMock.mockImplementation((p: 'left' | 'right') =>
+      p === 'right'
+        ? { volumeId: 'network', volumePath: 'smb://', path: '/Users/me/Downloads' }
+        : { volumeId: 'root', volumePath: '/', path: '/Users/me/elsewhere' },
+    )
+
+    await goToLatestDownload(makeExplorerStub())
+
+    expect(navigateMock).toHaveBeenCalledWith({ pane: 'left', to: { path: '/Users/me/Downloads' }, source: 'user' })
+    expect(setFocusedPaneMock).not.toHaveBeenCalled()
+    expect(moveCursorMock).toHaveBeenCalledWith('left', 'report.pdf')
+  })
+
+  it('does NOT count an MTP pane whose path string matches the local dir', async () => {
+    goToLatestDownloadMock.mockResolvedValue({
+      status: 'ok',
+      data: { path: '/Users/me/Downloads/report.pdf', parentDir: '/Users/me/Downloads', fileName: 'report.pdf' },
+    })
+    getFocusedPaneMock.mockReturnValue('left')
+    // MTP device volume: volumePath is an `mtp://…` URL, so the local Downloads
+    // path is not on it — `isPathOnVolume` rejects the match.
+    getPaneLocationMock.mockImplementation((p: 'left' | 'right') =>
+      p === 'right'
+        ? { volumeId: 'mtp-0-1', volumePath: 'mtp://mtp-0-1/65537', path: '/Users/me/Downloads' }
+        : { volumeId: 'root', volumePath: '/', path: '/Users/me/elsewhere' },
+    )
+
+    await goToLatestDownload(makeExplorerStub())
+
+    expect(navigateMock).toHaveBeenCalledWith({ pane: 'left', to: { path: '/Users/me/Downloads' }, source: 'user' })
+    expect(setFocusedPaneMock).not.toHaveBeenCalled()
+  })
+
   it('shows the empty INFO toast with the dedup id on GoToLatestError::Empty', async () => {
     goToLatestDownloadMock.mockResolvedValue({
       status: 'error',
@@ -128,6 +244,27 @@ describe('goToLatestDownload', () => {
     expect(moveCursorMock).not.toHaveBeenCalled()
   })
 
+  it('empty-toast "Go to Downloads" reuses a pane already showing Downloads, evaluated at click time', async () => {
+    goToLatestDownloadMock.mockResolvedValue({ status: 'error', error: { kind: 'empty' } })
+    downloadsWatcherStatusMock.mockResolvedValue({
+      status: 'ok',
+      data: { running: true, downloadsDir: '/Users/me/Downloads', fdaPending: false },
+    })
+    getFocusedPaneMock.mockReturnValue('left')
+
+    await goToLatestDownload(makeExplorerStub())
+
+    const [, options] = addToastMock.mock.calls[0] as unknown as [unknown, { props?: { onGoToDownloads: () => void } }]
+    // The other pane navigates to Downloads AFTER the toast was added, so the
+    // action must re-evaluate which pane shows the dir at CLICK time.
+    paneShows('right', '/Users/me/Downloads')
+    options.props?.onGoToDownloads()
+
+    // Pane reuse: focus the pane that shows Downloads, no fresh navigation.
+    expect(navigateMock).not.toHaveBeenCalled()
+    expect(setFocusedPaneMock).toHaveBeenCalledWith('right')
+  })
+
   it('shows the FDA INFO toast with the dedup id on GoToLatestError::WatcherUnavailable', async () => {
     goToLatestDownloadMock.mockResolvedValue({
       status: 'error',
@@ -200,15 +337,28 @@ describe('goToDownload', () => {
     navigateMock.mockReset().mockReturnValue({ status: 'started', settled: Promise.resolve() })
     moveCursorMock.mockReset().mockResolvedValue(undefined)
     getFocusedPaneMock.mockReset().mockReturnValue('left')
+    getPaneLocationMock.mockReset().mockReturnValue({ volumeId: 'root', volumePath: '/', path: '/Users/me/elsewhere' })
+    setFocusedPaneMock.mockReset()
   })
 
-  it('navigates the focused pane to parentDir and selects the file', async () => {
+  it('navigates the focused pane to parentDir and selects the file when neither pane shows it', async () => {
     await goToDownload(makeExplorerStub(), '/Users/me/Downloads', 'report.pdf')
 
     expect(navigateMock).toHaveBeenCalledWith({ pane: 'left', to: { path: '/Users/me/Downloads' }, source: 'user' })
     expect(moveCursorMock).toHaveBeenCalledWith('left', 'report.pdf')
   })
 
+  it('reuses the focused pane (cursor only) when it already shows the dir', async () => {
+    getFocusedPaneMock.mockReturnValue('left')
+    paneShows('left', '/Users/me/Downloads')
+
+    await goToDownload(makeExplorerStub(), '/Users/me/Downloads', 'report.pdf')
+
+    expect(navigateMock).not.toHaveBeenCalled()
+    expect(setFocusedPaneMock).not.toHaveBeenCalled()
+    expect(moveCursorMock).toHaveBeenCalledWith('left', 'report.pdf')
+  })
+
   it('does nothing when the explorer handle is missing (HMR / pre-mount)', async () => {
     await goToDownload(undefined, '/Users/me/Downloads', 'report.pdf')
 

apps/desktop/src/lib/downloads/go-to-latest.ts

@@ -3,16 +3,17 @@
  * palette, and the `go_to_latest_download` MCP tool).
  *
  * Calls the typed backend IPC and branches on the typed `GoToLatestError` enum —
- * no string matching. On success, navigates the focused pane to the file's
- * parent dir and moves the cursor to the file. On any error, surfaces a
- * single INFO toast using a stable dedup id so spamming ⌘J doesn't stack
- * copies.
+ * no string matching. On success, reveals the file in the best pane: if a pane
+ * already shows the file's parent dir, it reuses (and focuses) that pane instead
+ * of duplicating the view; otherwise it navigates the focused pane (see
+ * `revealFileInBestPane`). On any error, surfaces a single INFO toast using a
+ * stable dedup id so spamming ⌘J doesn't stack copies.
  */
 
 import { commands } from '$lib/ipc/bindings'
 import { addToast } from '$lib/ui/toast'
 import { getAppLogger } from '$lib/logging/logger'
-import { navigateToFileInPane } from '$lib/file-explorer/navigation/navigate-and-select'
+import { revealFileInBestPane, navigateToDirInBestPane } from '$lib/file-explorer/navigation/navigate-and-select'
 import type { ExplorerAPI } from '../../routes/(main)/explorer-api'
 
 import LatestDownloadEmptyToastContent from './LatestDownloadEmptyToastContent.svelte'
@@ -24,10 +25,12 @@ export { LATEST_DOWNLOAD_EMPTY_TOAST_ID, LATEST_DOWNLOAD_FDA_TOAST_ID }
 const log = getAppLogger('downloads')
 
 /**
- * Go to the latest download in the focused pane.
+ * Go to the latest download, reusing a pane that already shows its dir.
  *
  * Contract:
- * - Success: navigate the focused pane to `parentDir`, then select `fileName`.
+ * - Success: reveal `fileName` in `parentDir` via `revealFileInBestPane` (reuse
+ *   an open pane when one already shows the dir; otherwise navigate the focused
+ *   pane), then select `fileName`.
  * - `empty`: INFO toast with a "Go to Downloads" action (resolves the
  *   Downloads dir via `downloadsWatcherStatus` so the action knows where to go).
  * - `watcherUnavailable` / `downloadsDirUnresolved`: INFO toast with an
@@ -44,7 +47,7 @@ export async function goToLatestDownload(explorer: ExplorerAPI | undefined): Pro
 
   const result = await commands.goToLatestDownload()
   if (result.status === 'ok') {
-    await navigateToFileInPane(explorer, explorer.getFocusedPane(), result.data.parentDir, result.data.fileName)
+    await revealFileInBestPane(explorer, result.data.parentDir, result.data.fileName)
     return
   }
 
@@ -62,8 +65,9 @@ export async function goToLatestDownload(explorer: ExplorerAPI | undefined): Pro
 }
 
 /**
- * Go to a SPECIFIC downloaded file (parent dir + file name) in the focused
- * pane, bypassing the latest-in-ring lookup.
+ * Go to a SPECIFIC downloaded file (parent dir + file name), bypassing the
+ * latest-in-ring lookup. Reuses a pane that already shows the dir
+ * (`revealFileInBestPane`) rather than duplicating the view.
  *
  * `goToLatestDownload` consults the watcher's ring + scan fallback. The
  * downloads toast already knows the path it's for; jumping to the
@@ -83,7 +87,7 @@ export async function goToDownload(
     log.debug('goToDownload: no explorer; skipping (HMR or pre-mount)')
     return
   }
-  await navigateToFileInPane(explorer, explorer.getFocusedPane(), parentDir, fileName)
+  await revealFileInBestPane(explorer, parentDir, fileName)
 }
 
 async function showEmptyToast(explorer: ExplorerAPI): Promise<void> {
@@ -92,18 +96,15 @@ async function showEmptyToast(explorer: ExplorerAPI): Promise<void> {
   // the prop closure logs and bails.
   const status = await commands.downloadsWatcherStatus()
   const downloadsDir = status.status === 'ok' ? status.data.downloadsDir : null
-  // Snapshot the focused pane + Downloads dir at toast-add time so a later
-  // pane focus change doesn't redirect the action somewhere unexpected.
-  const focusedPane = explorer.getFocusedPane()
+  // Snapshot the Downloads dir at toast-add time (it won't change), but pick the
+  // target pane at CLICK time: `navigateToDirInBestPane` re-evaluates which pane
+  // shows the dir then, since pane contents may shift while the toast sits there.
   const onGoToDownloads = () => {
     if (!downloadsDir) {
       log.warn('Go to Downloads pressed but Downloads dir is unresolved; no action')
       return
     }
-    const result = explorer.navigate({ pane: focusedPane, to: { path: downloadsDir }, source: 'user' })
-    if (result.status === 'refused') {
-      log.warn('Go to Downloads: navigate refused: {reason}', { reason: result.reason.message })
-    }
+    void navigateToDirInBestPane(explorer, downloadsDir)
   }
   addToast(LatestDownloadEmptyToastContent, {
     id: LATEST_DOWNLOAD_EMPTY_TOAST_ID,