fix(windows): canonicalize native watch paths

packages/util/paths/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/util/paths/README.md
-README.md: 2b3272e019ef2f37386da9156b06a5c151836d8c
-README.zh.md: 7fe0ec04117ae439ade653cefd1c8f5da094d8fd
+README.md: 8d10ed855a37f1205f87420b3f36f45b10e65bd3
+README.zh.md: ed3ca377bd48252fe0ef3f95186dc6eb1fb6e6a0

packages/util/paths/README.md

@@ -18,9 +18,13 @@ Shared filesystem path helpers for DeepSeek Harness user data.
 
 `expandHomePath()` expands `~`, `~/...`, and Windows-style `~\...` prefixes against the operating-system home directory. It leaves non-tilde paths and `~user/...` untouched.
 
+## Watch paths
+
+`canonicalizeWatchPath()` gives a native filesystem watcher one stable spelling of its target. It resolves the deepest existing ancestor through `fs.realpath()` and restores any missing suffix, so a file or directory may still be watched before it is created. In particular, Windows 8.3 aliases cannot be mixed with the long paths emitted by the native watcher backend.
+
 This package is intentionally small and harness-dep-free so product packages can share user-data path conventions without depending on one another.
 
 ## Known Limitations and Deferred Work
 
 - **Expansion is deliberately narrow** — only bare `~`, `~/...`, and `~\...` use the current operating-system home; named-user forms such as `~alice/...`, environment variables, and shell expressions remain unchanged.
-- **Helpers do not touch the filesystem** — callers still own directory creation, existence checks, permissions, and trust policy for the resulting path.
+- **Canonicalization reads but never mutates** — `canonicalizeWatchPath()` performs `realpath` probes and propagates errors other than absence; callers still own directory creation, permissions, and trust policy for the resulting path.

packages/util/paths/README.zh.md

@@ -18,9 +18,13 @@ DeepSeek Harness 用户数据的共享文件系统路径辅助工具。
 
 `expandHomePath()` 使用操作系统主目录展开 `~`、`~/...` 和 Windows 风格的 `~\...` 前缀。它会保留非波浪号路径和 `~user/...` 原样不变。
 
+## 监听路径
+
+`canonicalizeWatchPath()` 为原生文件系统 watcher 提供一种稳定的目标路径表示。它通过 `fs.realpath()` 解析层级最深的现有祖先路径，再拼回缺失的后缀，因此即使文件或目录尚未创建也仍可监听。尤其是，Windows 8.3 别名不能与原生 watcher 后端发出的长路径混用。
+
 该包刻意保持规模小且不依赖 harness，以便产品包共享用户数据路径约定，而不必彼此依赖。
 
 ## 已知限制与暂缓事项
 
 - **展开范围刻意保持狭窄**：只有单独的 `~`、`~/...` 和 `~\...` 使用当前操作系统主目录；`~alice/...` 等指定用户的形式、环境变量和 shell 表达式保持不变。
-- **辅助工具不会操作文件系统**：调用方仍负责目录创建、存在性检查、权限，以及对结果路径应用信任策略。
+- **规范化会读取，但绝不修改**：`canonicalizeWatchPath()` 会执行 `realpath` 探测，并传播除路径不存在以外的错误；调用方仍负责目录创建、权限，以及对结果路径应用信任策略。

packages/util/paths/src/index.ts

@@ -4,8 +4,9 @@
  * @module @deepseek-ai/dsh-paths
  */
 
+import { realpath } from 'node:fs/promises'
 import { homedir } from 'node:os'
-import { join, resolve } from 'node:path'
+import { basename, dirname, join, resolve } from 'node:path'
 
 /** Directory name for the default DeepSeek Harness home under the OS home. */
 export const DSH_HOME_DIR_NAME = '.dsh'
@@ -16,6 +17,33 @@ export const DEFAULT_DSH_HOME_DISPLAY = `~/${DSH_HOME_DIR_NAME}`
 /** Environment variable that overrides the default DeepSeek Harness home. */
 export const DSH_HOME_ENV = 'DSH_HOME'
 
+/**
+ * Give a native filesystem watcher one canonical spelling of a path, even
+ * when its final components do not exist yet. The deepest existing ancestor
+ * is resolved through {@link realpath}; the missing suffix is then restored.
+ * This prevents Windows short-name aliases from being mixed with long paths
+ * emitted by the native watcher backend.
+ * @param path - Watch target or root, resolved against the current directory.
+ * @returns the target with its existing ancestor canonicalized.
+ * @throws when ancestor traversal encounters an error other than absence.
+ */
+export async function canonicalizeWatchPath(path: string): Promise<string> {
+  let current = resolve(path)
+  const missing: string[] = []
+  while (true) {
+    try {
+      return join(await realpath(current), ...missing.reverse())
+    } catch (error) {
+      if ((error as NodeJS.ErrnoException).code !== 'ENOENT') throw error
+      const parent = dirname(current)
+      /* v8 ignore next -- a filesystem root exists, so traversal resolves before this guard */
+      if (parent === current) throw error
+      missing.push(basename(current))
+      current = parent
+    }
+  }
+}
+
 /**
  * Resolve the default DeepSeek Harness home using Node's platform path rules.
  * @returns the absolute default harness home path.

packages/util/paths/tests/paths.spec.ts

@@ -1,9 +1,11 @@
-import { homedir } from 'node:os'
+import { mkdir, mkdtemp, realpath, rm, symlink, writeFile } from 'node:fs/promises'
+import { homedir, tmpdir } from 'node:os'
 import { join, resolve } from 'node:path'
 import { afterEach, describe, expect, it, vi } from 'vitest'
 import {
   DEFAULT_DSH_HOME_DISPLAY,
   DSH_HOME_DIR_NAME,
+  canonicalizeWatchPath,
   defaultDshHome,
   dshHomeDisplay,
   dshHomePath,
@@ -53,4 +55,22 @@ describe('dsh path helpers', () => {
     expect(dshHomeDisplay(resolve(defaultDshHome()))).toBe('~/.dsh')
     expect(dshHomeDisplay('/some/other/root')).toBe('$DSH_HOME')
   })
+
+  it('canonicalizes a watcher ancestor while preserving a missing suffix', async () => {
+    const root = await mkdtemp(join(tmpdir(), 'dsh-watch-path-'))
+    const target = join(root, 'target')
+    const alias = join(root, 'alias')
+    try {
+      await mkdir(target)
+      await symlink(target, alias, process.platform === 'win32' ? 'junction' : 'dir')
+      await expect(canonicalizeWatchPath(join(alias, 'later', 'config.yml'))).resolves.toBe(
+        join(await realpath(target), 'later', 'config.yml'),
+      )
+      const file = join(root, 'file')
+      await writeFile(file, 'not a directory')
+      await expect(canonicalizeWatchPath(join(file, 'child'))).rejects.toMatchObject({ code: 'ENOTDIR' })
+    } finally {
+      await rm(root, { recursive: true, force: true })
+    }
+  })
 })