feat(host): navigations land selection-anchored — crumb jumps step back a pane instead of collapsing

packages/host/directory-picker-browse/README.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/host/directory-picker-browse/README.md
-README.md: 7813e0e9c589d1f37471b08ebafcf08878cbf768
-README.zh.md: 46538ed6f1cf23357cc4f8e289a8117d0e5e017d
+README.md: 51e27115b5179796810c19b618b08a3523de8d10
+README.zh.md: 4caeff1c2ebfea2c12e6bb598dae2c34f2e34d84

packages/host/directory-picker-browse/README.md

@@ -6,7 +6,7 @@ The **in-app browsing backend** of the [directory-picker seam](../directory-pick
 
 Behavior facts: listings return **directories only**, name-sorted, with symlinks-to-directories followed (broken/cyclic links skipped — the probe `stat` failing means "not enterable") and a host-owned `hidden` flag (POSIX dot convention) left for the client to act on; `crumbs` is the root-to-target ancestor chain, the root crumb labeled by its full path (`/`, `C:\`); an absent `list` path means the host account's home directory. `createDirectory` is non-recursive (a missing parent is a real failure, not a level to invent) and validates the name as a single non-blank segment even when called directly, mirroring the wire schema's fence. Both primitives reject an explicit path that is not fully qualified — relative forms, and on Windows the rooted drive-less forms (`\foo`, `/foo`) and incomplete UNC prefixes (`\\`, `\\server`) that `isAbsolute` accepts — with `directory-unreadable`/`directory-create-failed`, instead of letting `resolve` rebase it under the host process cwd or current drive. One `list` call returns at most `maxEntries` rows (config, default 1000 — the bound GitHub's web UI applies to directory listings), and the level streams through a bounded window so memory stays O(maxEntries) no matter how many children the directory holds: a cut level keeps the name-sorted head, counts hidden rows against the bound, probes only windowed candidates, and reports `truncated: true` so the client can say the level is incomplete (a windowed broken symlink is not backfilled from beyond the window — the eviction already marks the level truncated); window insertion is binary with an O(1) full-window tail rejection, and `list` threads the caller's `AbortSignal` so a disconnect or timeout stops the scan instead of letting it outlive the caller. Failures throw the seam's typed `DirectoryPickerError`. Policy rationale: [the directory-picker capability seam Agent Note](../../../.agents/notes/implemented/architecture/2026-07-28-directory-picker-capability-seam.md).
 
-**Dual-face package**: the browser half (`./client`) fills [ui-workspace's](../../client/ui-workspace/README.md) two directory-flow holes with the in-app **Select Workspace Directory** dialog (figma `Harness` 813-23126 family — Miller two-column view; breadcrumb with a click-to-edit path zone whose editor seeds a trailing separator, prefix-filters the listed level from the draft's final segment while typing (case-insensitively, over the listed — possibly truncated — rows only; Enter still navigates by the exact text), and cancels on Escape or when focus leaves the dialog card (window/tab switches and in-card focus moves keep the draft); a fixed-label show-hidden footer toggle over the host's `hidden` flags, with a dot-led typed prefix revealing its matches and the current selection exempt from both filters; nested New-folder dialog), driving `host.listDirectory`/`host.createDirectory` and registering its own locale namespace (`directory-browser`, zh default / en). One cordis.yml row therefore composes both sides of the browse interaction; the client carries no capability-kind branching, and mounting a second flow package fails at load (the holes are `single` kind).
+**Dual-face package**: the browser half (`./client`) fills [ui-workspace's](../../client/ui-workspace/README.md) two directory-flow holes with the in-app **Select Workspace Directory** dialog (figma `Harness` 813-23126 family — Miller two-column view whose navigations land selection-anchored: a crumb jump or a submitted path lists the target's parent level with the target selected, so stepping back keeps two panes while the display root keeps the single wide level; breadcrumb with a click-to-edit path zone whose editor seeds a trailing separator, prefix-filters the listed level from the draft's final segment while typing (case-insensitively, over the listed — possibly truncated — rows only; Enter still navigates by the exact text), and cancels on Escape or when focus leaves the dialog card (window/tab switches and in-card focus moves keep the draft); a fixed-label show-hidden footer toggle over the host's `hidden` flags, with a dot-led typed prefix revealing its matches and the current selection exempt from both filters; nested New-folder dialog), driving `host.listDirectory`/`host.createDirectory` and registering its own locale namespace (`directory-browser`, zh default / en). One cordis.yml row therefore composes both sides of the browse interaction; the client carries no capability-kind branching, and mounting a second flow package fails at load (the holes are `single` kind).
 
 ## Model Experience
 

packages/host/directory-picker-browse/README.zh.md

@@ -6,7 +6,7 @@
 
 行为事实：列举**只返回目录**、按名称排序，指向目录的符号链接会被跟随（断链／循环链接被跳过——探测 `stat` 失败即"不可进入"），并携带宿主判定的 `hidden` 标志（POSIX 点前缀约定），展示决策留给客户端；`crumbs` 是从根到目标的祖先链，根 crumb 以完整路径标注（`/`、`C:\`）；`list` 不带路径即列举宿主账户的家目录。`createDirectory` 不递归（父目录缺失是真实失败，不是要补造的层级），且即便被直接调用也把名称校验为单个非空段，与协议 schema 的栅栏一致。两个原语都拒绝非完全限定的显式路径——相对形态，以及 Windows 上 `isAbsolute` 会放行的无盘符有根形态（`\foo`、`/foo`）与不完整的 UNC 前缀（`\\`、`\\server`）——报 `directory-unreadable`／`directory-create-failed`，而不是任由 `resolve` 把它重定位到宿主进程 cwd 或当前盘符之下。单次 `list` 至多返回 `maxEntries` 行（配置项，默认 1000——GitHub 网页端对目录列举采用的同一上限），且层级以流式方式经过一个有界窗口，无论目录有多少子项内存都保持 O(maxEntries)：被截断的层级保留按名排序的头部、隐藏行计入上限、只探测窗口内候选，并报告 `truncated: true`，供客户端提示层级不完整（窗口内的断链符号链接不会从窗口外回填——发生过驱逐本身已把层级标记为截断）；窗口插入为二分查找、满窗尾部单次比较即拒绝，且 `list` 透传调用方的 `AbortSignal`，断连或超时会停止扫描而不是让它在调用方离开后继续。失败抛出 seam 的类型化 `DirectoryPickerError`。策略依据：[目录选择能力 seam Agent Note](../../../.agents/notes/implemented/architecture/2026-07-28-directory-picker-capability-seam.md)。
 
-**双面包**：browser half（`./client`）以应用内 **选择工作区目录** 对话框（figma `Harness` 813-23126 家族——Miller 双列视图；带点击即编辑路径区的面包屑，其编辑器预填尾随分隔符、输入时以草稿末段对所列层级做前缀过滤（不区分大小写，且仅作用于已列出、可能被截断的行；Enter 仍按确切文本导航）、按 Escape 或焦点离开对话框卡片即取消（窗口／标签页切换与卡片内焦点移动保留草稿）；基于宿主 `hidden` 标志、标签固定的"显示隐藏"footer 开关，键入以点开头的前缀会显出其匹配项，且当前选中项不受这两种过滤影响；嵌套新建文件夹对话框）填入 [ui-workspace](../../client/ui-workspace/README.md) 的两个目录流洞，驱动 `host.listDirectory`／`host.createDirectory`，并注册自己的 locale 命名空间（`directory-browser`，zh 默认／en）。因此一行 cordis.yml 同时组合浏览交互的两侧；client 侧不含任何能力 kind 分支，挂载第二个流程包会在加载期失败（洞为 `single` kind）。
+**双面包**：browser half（`./client`）以应用内 **选择工作区目录** 对话框（figma `Harness` 813-23126 家族——Miller 双列视图，其导航以选中项为锚落地：crumb 跳转或提交的路径会列出目标的父层级并选中目标，因此后退仍保持双栏，而展示根保持单个宽层级；带点击即编辑路径区的面包屑，其编辑器预填尾随分隔符、输入时以草稿末段对所列层级做前缀过滤（不区分大小写，且仅作用于已列出、可能被截断的行；Enter 仍按确切文本导航）、按 Escape 或焦点离开对话框卡片即取消（窗口／标签页切换与卡片内焦点移动保留草稿）；基于宿主 `hidden` 标志、标签固定的"显示隐藏"footer 开关，键入以点开头的前缀会显出其匹配项，且当前选中项不受这两种过滤影响；嵌套新建文件夹对话框）填入 [ui-workspace](../../client/ui-workspace/README.md) 的两个目录流洞，驱动 `host.listDirectory`／`host.createDirectory`，并注册自己的 locale 命名空间（`directory-browser`，zh 默认／en）。因此一行 cordis.yml 同时组合浏览交互的两侧；client 侧不含任何能力 kind 分支，挂载第二个流程包会在加载期失败（洞为 `single` kind）。
 
 ## 模型体验
 

packages/host/directory-picker-browse/src/client/DirectoryBrowser.tsx

@@ -214,24 +214,60 @@ export function DirectoryBrowser({ open, listDirectory, createDirectory, onOpen,
     return { seq, scan: listDirectory(path, controller.signal) }
   }, [supersede, listDirectory])
 
-  /** Replace the whole view with one freshly listed level (no selection). */
+  /**
+   * Replace the whole view with a freshly navigated level. Away from the
+   * display root the landing keeps the navigated directory SELECTED inside
+   * its parent level (left pane = parent, right pane = its children), so a
+   * crumb jump or a submitted path reads as stepping back one pane instead
+   * of collapsing to a single column; the display root (the home level, or
+   * a chain with no parent) keeps the single wide level.
+   */
   const navigate = useCallback((path?: string) => {
     const { seq, scan } = launchListing(path)
     setLoading(true)
     setError(null)
-    scan.then((next) => {
+    scan.then((target) => {
       if (seq !== requestSeq.current) return
-      setParent(next)
-      setSelected(null)
-      setChild(null)
-      setLoading(false)
-      setPathDraft(null)
+      const parentCrumb = target.crumbs.at(-2)
+      const anchor = target.crumbs.at(-1)
+      if (target.path === target.home || parentCrumb === undefined
+        /* v8 ignore next -- narrowing: the anchor crumb exists whenever a parent crumb does (root-to-target inclusive chain). */
+        || anchor === undefined) {
+        setParent(target)
+        setSelected(null)
+        setChild(null)
+        setLoading(false)
+        setPathDraft(null)
+        return
+      }
+      // Two-pane landing: the parent leg runs under the same supersession
+      // scope (a newer intent aborts it like the first leg).
+      const controller = new AbortController()
+      scanController.current = controller
+      listDirectory(parentCrumb.path, controller.signal).then((parentLevel) => {
+        if (seq !== requestSeq.current) return
+        setParent(parentLevel)
+        setSelected(anchor)
+        setChild(target)
+        setLoading(false)
+        setPathDraft(null)
+      }, () => {
+        if (seq !== requestSeq.current) return
+        // The target listed fine and is what the user asked for; a parent
+        // leg failure quietly falls back to the single-pane landing rather
+        // than surfacing an error for a level nobody requested.
+        setParent(target)
+        setSelected(null)
+        setChild(null)
+        setLoading(false)
+        setPathDraft(null)
+      })
     }, (reason: unknown) => {
       if (seq !== requestSeq.current) return
       setLoading(false)
       setError(failureText(reason))
     })
-  }, [launchListing])
+  }, [launchListing, listDirectory])
 
   // Editor-close focus parking (consumed by the refocus effect below the
   // miller-row ref): a pick parks on the selection's row, Enter and an

packages/host/directory-picker-browse/tests/directory-browser.spec.tsx

@@ -29,6 +29,13 @@ function listingFor(path?: string): DirectoryListing {
       ],
       truncated: false,
     },
+    '/': {
+      path: '/',
+      home: HOME,
+      crumbs: [{ name: '/', path: '/', hidden: false }],
+      entries: [{ name: 'home', path: '/home', hidden: false }],
+      truncated: false,
+    },
     [`${HOME}/.config`]: {
       path: `${HOME}/.config`,
       home: HOME,
@@ -198,6 +205,88 @@ describe('DirectoryBrowser', () => {
     expect(rowButton(screen.getByRole('listitem')).getAttribute('aria-current')).toBeNull()
   })
 
+  it('a crumb jump away from the root lands two-pane with the target selected', async () => {
+    mount()
+    await waitFor(() => { expect(screen.getByRole('listitem')).toBeTruthy() })
+    fireEvent.click(rowButton(screen.getByRole('listitem')))
+    await waitFor(() => { expect(columns()).toHaveLength(2) })
+    fireEvent.click(rowButton(within(columns()[1]!).getByRole('listitem')))
+    await waitFor(() => { expect(screen.getByRole('button', { name: 'harness' })).toBeTruthy() })
+    // Jumping to the Documents crumb is a step BACK one pane, not a
+    // collapse: Documents stays selected in the home level, its children
+    // stay on the right.
+    fireEvent.click(screen.getByRole('button', { name: 'Documents' }))
+    await waitFor(() => {
+      expect(rowButton(within(columns()[0]!).getByRole('listitem')).getAttribute('aria-current')).toBe('true')
+    })
+    expect(columns()).toHaveLength(2)
+    expect(within(columns()[0]!).getByText('Documents')).toBeTruthy()
+    expect(within(columns()[1]!).getByText('harness')).toBeTruthy()
+  })
+
+  it('a navigation to the filesystem root keeps the single wide level', async () => {
+    mount()
+    await waitFor(() => { expect(screen.getByRole('listitem')).toBeTruthy() })
+    fireEvent.click(screen.getByRole('button', { name: 'browser.editPath' }))
+    fireEvent.change(screen.getByLabelText<HTMLInputElement>('browser.editPath'), { target: { value: '/' } })
+    fireEvent.keyDown(screen.getByLabelText('browser.editPath'), { key: 'Enter' })
+    // A one-crumb chain has no parent level to show on the left.
+    await waitFor(() => { expect(screen.getByRole('listitem').textContent).toBe('home') })
+    expect(columns()).toHaveLength(1)
+  })
+
+  it('drops a parent leg that settles after a newer intent, resolving or rejecting', async () => {
+    const settlers: { resolve: (value: DirectoryListing) => void; reject: (reason: unknown) => void }[] = []
+    const listDirectory = vi.fn(async (path?: string) => {
+      if (path === HOME) {
+        return new Promise<DirectoryListing>((resolve, reject) => { settlers.push({ resolve, reject }) })
+      }
+      return listingFor(path)
+    })
+    mount({ listDirectory })
+    await waitFor(() => { expect(screen.getByRole('listitem')).toBeTruthy() })
+    // Enter lands the target leg; the parent leg hangs. Escape supersedes
+    // the landing, and the late parent RESOLUTION must change nothing.
+    fireEvent.click(screen.getByRole('button', { name: 'browser.editPath' }))
+    fireEvent.change(screen.getByLabelText<HTMLInputElement>('browser.editPath'), { target: { value: DOCS } })
+    fireEvent.keyDown(screen.getByLabelText('browser.editPath'), { key: 'Enter' })
+    await waitFor(() => { expect(settlers).toHaveLength(1) })
+    fireEvent.keyDown(screen.getByLabelText('browser.editPath'), { key: 'Escape' })
+    await act(async () => { settlers[0]!.resolve(listingFor(HOME)) })
+    expect(columns()).toHaveLength(1)
+    expect(screen.getByRole('listitem').textContent).toBe('Documents')
+    // Same shape, late parent REJECTION: equally silent.
+    fireEvent.click(screen.getByRole('button', { name: 'browser.editPath' }))
+    fireEvent.change(screen.getByLabelText<HTMLInputElement>('browser.editPath'), { target: { value: DOCS } })
+    fireEvent.keyDown(screen.getByLabelText('browser.editPath'), { key: 'Enter' })
+    await waitFor(() => { expect(settlers).toHaveLength(2) })
+    fireEvent.keyDown(screen.getByLabelText('browser.editPath'), { key: 'Escape' })
+    await act(async () => { settlers[1]!.reject(new Error('late')) })
+    expect(columns()).toHaveLength(1)
+    expect(screen.queryByRole('alert')).toBeNull()
+  })
+
+  it('falls back to the single-pane landing when the parent leg of a navigation fails', async () => {
+    const listDirectory = vi.fn(async (path?: string) => {
+      // The initial open lists home through the absent-path form; only the
+      // parent leg names HOME explicitly.
+      if (path === HOME) {
+        throw new DirectoryBrowseError({ code: 'directory-unreadable', message: 'parent gone', details: { path } })
+      }
+      return listingFor(path)
+    })
+    mount({ listDirectory })
+    await waitFor(() => { expect(screen.getByRole('listitem')).toBeTruthy() })
+    fireEvent.click(screen.getByRole('button', { name: 'browser.editPath' }))
+    fireEvent.change(screen.getByLabelText<HTMLInputElement>('browser.editPath'), { target: { value: DOCS } })
+    fireEvent.keyDown(screen.getByLabelText('browser.editPath'), { key: 'Enter' })
+    // The target listed fine; the failed parent leg neither blocks the
+    // landing nor surfaces an error for a level nobody asked to see.
+    await waitFor(() => { expect(screen.getByRole('listitem').textContent).toBe('harness') })
+    expect(columns()).toHaveLength(1)
+    expect(screen.queryByRole('alert')).toBeNull()
+  })
+
   it('opens the selection, else the listed level; Cancel closes; busy freezes Open', async () => {
     const b = mount()
     await waitFor(() => { expect(screen.getByRole('listitem')).toBeTruthy() })
@@ -225,8 +314,11 @@ describe('DirectoryBrowser', () => {
     expect(input.value).toBe(`${HOME}/`)
     fireEvent.change(input, { target: { value: DOCS } })
     fireEvent.keyDown(input, { key: 'Enter' })
-    await waitFor(() => { expect(screen.getByRole('listitem').textContent).toBe('harness') })
-    expect(columns()).toHaveLength(1)
+    // Away from the root a navigation lands two-pane: the target selected
+    // in its parent level, its own children on the right.
+    await waitFor(() => { expect(columns()).toHaveLength(2) })
+    expect(rowButton(within(columns()[0]!).getByRole('listitem')).getAttribute('aria-current')).toBe('true')
+    expect(within(columns()[1]!).getByText('harness')).toBeTruthy()
     // The submitted navigation unmounted the focused input; focus parks on
     // the crumb edit zone that replaced it.
     expect(document.activeElement).toBe(screen.getByRole('button', { name: 'browser.editPath' }))
@@ -234,7 +326,9 @@ describe('DirectoryBrowser', () => {
     const again = screen.getByLabelText<HTMLInputElement>('browser.editPath')
     fireEvent.change(again, { target: { value: '   ' } })
     fireEvent.keyDown(again, { key: 'Enter' })
-    expect(b.listDirectory).toHaveBeenCalledTimes(2)
+    // Initial home + the DOCS target leg + its parent leg; the blank draft
+    // added none.
+    expect(b.listDirectory).toHaveBeenCalledTimes(3)
     fireEvent.keyDown(again, { key: 'Escape' })
     expect(screen.queryByLabelText('browser.editPath', { selector: 'input' })).toBeNull()
     // Escape with focus in the input parks focus on the returning edit zone.
@@ -945,11 +1039,13 @@ describe('DirectoryBrowser', () => {
     b.listDirectory.mockReturnValueOnce(slow)
     fireEvent.click(screen.getByRole('button', { name: 'browser.home' }))
     fireEvent.click(within(screen.getByRole('navigation')).getByRole('button', { name: 'Documents' }))
-    await waitFor(() => { expect(screen.getByRole('listitem').textContent).toBe('harness') })
+    // The newer jump lands two-pane: Documents selected at home, children right.
+    await waitFor(() => { expect(within(columns()[1]!).getByText('harness')).toBeTruthy() })
     resolveSlow(listingFor(undefined))
     await new Promise(settle => setTimeout(settle, 0))
-    // The stale home listing did not replace the newer Documents level.
-    expect(screen.getByRole('listitem').textContent).toBe('harness')
+    // The stale home listing did not replace the newer Documents landing.
+    expect(columns()).toHaveLength(2)
+    expect(within(columns()[1]!).getByText('harness')).toBeTruthy()
   })
 
   it('names the create target by its path when the level reports no crumbs', async () => {