feat(skill): hot-refresh skill catalogs

packages/skill/skill-local/README.i18n.yaml

@@ -1,6 +1,6 @@
 # Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
 # 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
-README.md: c488fdc4b1d97b5aa1113e41a470484063526ded
-README.zh.md: 796c814a3c4064d545a966465caf6f99e9dd8601
+#   pnpm run verify-translation-pairing --write packages/skill/skill-local/README.md
+README.md: 0e25e5a964902d84edbd2ca53f4e63b5f9c21065
+README.zh.md: 19b1091ec08eec9f844f339cdd0226309735ca09

packages/skill/skill-local/README.md

@@ -17,6 +17,12 @@ Requires `ctx.skills` (`inject: ['skills']`).
 | `dshHome` | `$DSH_HOME` or `~/.dsh` | DeepSeek Harness config root resolved by [`@deepseek-ai/dsh-paths`](../../util/paths/README.md); scans `skills` under this directory. |
 | `agentsHome` | `$DSH_AGENTS_HOME` or `~/.agents` | Shared agent config root scanned for compatible skills. |
 | `customSkillDirs` | `[]` | Additional local skill roots scanned after project roots and before user roots. |
+| `watch` | `true` | Watch host-local roots and invalidate the local provider when catalog membership or frontmatter may have changed. |
+| `watchUsePolling` | `false` | Use Chokidar polling instead of native events for existing skill roots. |
+| `watchStabilityThresholdMs` | `200` | Stable-write window for Chokidar `add` and `change` events. |
+| `watchPollIntervalMs` | `100` | Chokidar polling/stability interval and missing-path probe interval. |
+| `watchMaxProjects` | `128` | Maximum distinct project roots retained in the watcher LRU. |
+| `watchFollowSymlinks` | `true` | Follow symbolic links while watching existing roots. |
 
 ## Discovery
 
@@ -32,23 +38,34 @@ Default roots are resolved in this provider's rank order:
 
 The project root is the nearest ancestor containing `.git`; without one, the current cwd is used. The user DSH root skips its `.system` child so system-owned directories are not treated as normal user skills. This provider supplies project and user skills; another provider may supply built-in system skills.
 
-When `ctx.fs` is available, discovery lists roots through `ctx.fs.listDir`, reads skill files through `ctx.fs.readText`, and probes `.git` through the filesystem service. Full skill loads forward the lookup abort signal to filesystem metadata and content reads. Without a filesystem service, the provider falls back to abortable Node filesystem I/O so minimal local contexts can still load skills. Missing, unreadable, or malformed skill files warn and skip instead of failing the whole request.
+When `ctx.fs` is available, discovery lists roots through `ctx.fs.listDir`, reads skill files through `ctx.fs.readText`, and probes `.git` through the filesystem service. Full skill loads forward the lookup abort signal to filesystem metadata and content reads. Without a filesystem service, the provider falls back to abortable Node filesystem I/O so minimal local contexts can still load skills. Confirmed missing paths are valid empty state, malformed or non-text entries warn and skip, and unexpected discovery/read failures make the registry snapshot incomplete rather than replacing a last-good model catalog with a misleading deletion.
+
+## Catalog Change Detection
+
+Existing skill roots are watched with Chokidar. The provider observes direct bundle directory additions/removals, flat Markdown additions/removals, and direct `SKILL.md` additions/removals/changes; `change` exists to rediscover catalog frontmatter such as `name` and `description`. Changes below `references`, `scripts`, `assets`, or other bundle resources do not invalidate the catalog. Events delivered in the same microtask batch collapse to one provider invalidation.
+
+A root that does not exist is followed from the nearest existing ancestor one missing path segment at a time. The next segment is probed with `fs.watchFile`; once `.agents`, `skills`, or the configured root appears, observation advances until Chokidar can attach to the real root. Root deletion reverses this process, so deleting and recreating an entire skills directory remains observable. Project-scoped watchers are bounded by `watchMaxProjects`; revisiting an evicted project reattaches observation during discovery.
+
+The first-party filesystem `write` and `edit` tools also synchronously invalidate the provider through `fs/observed` when their target could affect a watched skill entry. This fast path makes the next model step observe its own filesystem mutation without waiting for the host watcher. External IDE, Git, shell, and process changes rely on Chokidar or the missing-path probe. Startup/runtime watcher failures are logged, make the current provider observation incomplete, and are retried; effect teardown closes every watcher and contains late callbacks.
 
 ## Skill Format
 
 Skills can be single-level directory bundles (`<name>/SKILL.md`) or flat Markdown files (`<name>.md`). Nested `**/SKILL.md` discovery is intentionally not part of v1. Frontmatter is parsed as YAML with the `yaml` package; it requires `name` and `description`, while `whenToUse`, `disableModelInvocation`, and `metadata` are optional. Names must be kebab-case.
 
+The catalog and body have separate lifecycles. Discovery parses frontmatter to produce the summary. Every `skill(name)` load rereads and reparses the current file, so body edits need no hash, revision, cache invalidation, or proactive model notification. A frontmatter rename between discovery and loading rejects the stale name and invalidates the provider; the next catalog observation publishes the new name.
+
 ## Model Experience
 
-Indirectly, through `dsh-tool-skill`, which renders this provider's invocable names and capped descriptions into the session-prefix catalog and a selected instruction body plus resource-base guidance into retained tool history while paths, provider ranks, and disabled skills remain hidden.
+Indirectly, through `dsh-tool-skill`, which renders this provider's invocable names and capped descriptions into the initial or replacement catalog and a selected current instruction body plus resource-base guidance into retained tool history while paths, provider ranks, and disabled skills remain hidden.
 
 #### KV Cache effect
 
-No direct invalidation; the named consumer owns any request-prefix changes.
+Watcher invalidation can cause the named consumer to append a replacement catalog after the reusable session prefix. Body-only edits leave the catalog digest unchanged.
 
 ## Known Limitations and Deferred Work
 
 - **Discovery is one level deep** — only `<root>/<name>/SKILL.md` and `<root>/<name>.md` are recognized; nested skill trees and package manifests are ignored.
 - **Project scope is the nearest `.git` ancestor** — workspaces without that marker fall back to the supplied cwd, with no alternate project-root marker or monorepo subproject selection.
-- **Unreadable or malformed entries disappear with a warning** — the model catalog receives no per-skill diagnostic and cannot distinguish an absent skill from a skipped one.
-- **No filesystem watching** — edits rely on the registry cache being evicted or invalidated by provider reload before a previously collected cwd is rediscovered.
+- **Malformed entries disappear with a warning** — the model catalog receives no per-skill diagnostic and cannot distinguish an absent skill from an invalid one; unexpected I/O failures preserve the last-good catalog instead.
+- **Missing-root observation polls one path segment** — roots absent at startup use `fs.watchFile` at `watchPollIntervalMs` until Chokidar can attach, trading bounded detection latency for reliable creation detection across IDE, Git, and shell workflows.
+- **No body revision protocol** — a loaded body is ordinary retained tool history; later file edits affect later calls but neither rewrite old results nor announce that the body changed.

packages/skill/skill-local/README.zh.md

@@ -17,6 +17,12 @@
 | `dshHome` | `$DSH_HOME` or `~/.dsh` | 由 [`@deepseek-ai/dsh-paths`](../../util/paths/README.md) 解析的 DeepSeek Harness 配置根；扫描该目录下的 `skills`。 |
 | `agentsHome` | `$DSH_AGENTS_HOME` or `~/.agents` | 为兼容 skill 扫描的共享 agent 配置根。 |
 | `customSkillDirs` | `[]` | 在项目根之后、用户根之前扫描的其他本地 skill 根。 |
+| `watch` | `true` | 监视宿主本地根，并在目录成员或 frontmatter 可能发生变化时使本地提供方失效。 |
+| `watchUsePolling` | `false` | 对现有 skill 根使用 Chokidar 轮询，而不是原生事件。 |
+| `watchStabilityThresholdMs` | `200` | Chokidar `add` 和 `change` 事件的稳定写入窗口。 |
+| `watchPollIntervalMs` | `100` | Chokidar 轮询／稳定性间隔和缺失路径探测间隔。 |
+| `watchMaxProjects` | `128` | watcher LRU 中保留的不同项目根数量上限。 |
+| `watchFollowSymlinks` | `true` | 监视现有根时跟随符号链接。 |
 
 ## 发现
 
@@ -32,23 +38,34 @@
 
 项目根是包含 `.git` 的最近祖先；如果不存在，则使用当前 cwd。用户 DSH 根会跳过其 `.system` 子级，因此系统所有目录不会被当作普通用户 skill。该提供方提供项目和用户 skill；其他提供方可提供内置系统 skill。
 
-当 `ctx.fs` 可用时，发现通过 `ctx.fs.listDir` 列出根，通过 `ctx.fs.readText` 读取 skill 文件，并通过文件系统服务探测 `.git`。完整 skill 加载会将查找中止信号转发给文件系统元数据和内容读取。如果没有文件系统服务，提供方回退到可中止的 Node 文件系统 I/O，使最小本地上下文仍能加载 skill。缺失、不可读或格式错误的 skill 文件会警告并跳过，而不会使整个请求失败。
+当 `ctx.fs` 可用时，发现通过 `ctx.fs.listDir` 列出根，通过 `ctx.fs.readText` 读取 skill 文件，并通过文件系统服务探测 `.git`。完整 skill 加载会将查找中止信号转发给文件系统元数据和内容读取。如果没有文件系统服务，提供方回退到可中止的 Node 文件系统 I/O，使最小本地上下文仍能加载 skill。已确认缺失的路径属于有效空状态；格式错误或非文本条目会警告并跳过；意外的发现或读取失败会使注册表快照不完整，系统不会因此用看似发生删除的结果替换上一份可用模型目录。
+
+## 目录变更检测
+
+现有 skill 根由 Chokidar 监视。提供方会观察直属 bundle 目录的添加／移除、平铺 Markdown 文件的添加／移除，以及直接 `SKILL.md` 的添加／移除／变更；`change` 事件用于重新发现 `name`、`description` 等目录 frontmatter。`references`、`scripts`、`assets` 或其他 bundle 资源下的变更不会使目录失效。同一微任务批次内送达的事件会合并为一次提供方失效。
+
+不存在的根会从最近的现有祖先开始，每次沿一个缺失路径段跟踪。系统使用 `fs.watchFile` 探测下一段；当 `.agents`、`skills` 或已配置的根出现后，观察会逐级推进，直至 Chokidar 可以附加到真实根。根删除时，该过程反向执行，因此删除再重建整个 skills 目录仍可被观察到。按项目划分的 watcher 数量受 `watchMaxProjects` 限制；再次访问已被驱逐的项目时，发现阶段会重新附加观察。
+
+如果第一方文件系统 `write` 和 `edit` 工具的目标可能影响受监视的 skill 条目，它们还会通过 `fs/observed` 同步使提供方失效。这条快速路径让模型的下一个步骤无需等待宿主 watcher，即可观察到自身的文件系统变更。外部 IDE、Git、shell 和进程产生的变更依赖 Chokidar 或缺失路径探测。watcher 启动或运行时失败会被记录，使提供方的当前观察不完整，并触发重试；effect 释放会关闭所有 watcher，并收束延迟回调。
 
 ## Skill 格式
 
 Skill 可以是单层目录 bundle（`<name>/SKILL.md`），也可以是平铺 Markdown 文件（`<name>.md`）。v1 刻意不包含嵌套 `**/SKILL.md` 发现。Frontmatter 使用 `yaml` 包解析为 YAML；它要求 `name` 和 `description`，而 `whenToUse`、`disableModelInvocation` 和 `metadata` 可选。名称必须使用 kebab-case。
 
+目录与正文具有独立的生命周期。发现阶段解析 frontmatter 以生成概述。每次 `skill(name)` 加载都会重新读取并解析当前文件，因此正文编辑不需要 hash、修订号、缓存失效或主动通知模型。若在发现与加载之间重命名 frontmatter，系统会拒绝陈旧名称并使提供方失效；下一次目录观察会发布新名称。
+
 ## 模型体验
 
-通过 `dsh-tool-skill` 间接影响模型。它将该提供方的可调用名称和有上限描述渲染到会话前缀目录中，并将所选指令正文与资源基底指引渲染到已保留工具历史中；路径、提供方 rank 和已禁用 skill 仍被隐藏。
+通过 `dsh-tool-skill` 间接影响模型。它将该提供方的可调用名称和有上限描述渲染到初始目录或替换目录中，并将所选当前指令正文与资源基底指引渲染到已保留工具历史中；路径、提供方 rank 和已禁用 skill 仍被隐藏。
 
 #### KV 缓存影响
 
-不直接导致失效；指定的消费方负责其引起的任何请求前缀变更。
+watcher 触发的失效可促使指定的消费方在可复用会话前缀之后追加替换目录。仅涉及正文的编辑不会改变目录 digest。
 
 ## 已知限制与待完成工作
 
 - **发现深度为一层**：只识别 `<root>/<name>/SKILL.md` 和 `<root>/<name>.md`；忽略嵌套 skill 树和包 manifest。
 - **项目范围为最近 `.git` 祖先**：没有该标记的工作区回退到提供的 cwd，不支持其他项目根标记或 monorepo 子项目选择。
-- **不可读或格式错误的条目会随警告消失**：模型目录不会收到每个 skill 的诊断，无法区分缺失的 skill 与被跳过的 skill。
-- **无文件系统 watcher**：先前已收集 cwd 重新发现之前，编辑操作依赖注册表缓存被驱逐，或因提供方重新加载而失效。
+- **格式错误的条目会随警告消失**：模型目录不会收到每个 skill 的诊断，无法区分缺失的 skill 与无效的 skill；意外 I/O 失败则会保留最后一份可用目录。
+- **缺失根观察每次轮询一个路径段**：启动时不存在的根会使用 `fs.watchFile` 按 `watchPollIntervalMs` 轮询，直至 Chokidar 可以附加；这以有界检测延迟换取跨 IDE、Git 和 shell 工作流的可靠创建检测。
+- **无正文修订协议**：已加载的正文是普通的已保留工具历史；后续文件编辑会影响后续调用，但既不会改写旧结果，也不会通知正文已发生变化。

packages/skill/skill-local/package.json

@@ -34,6 +34,7 @@
     "cordis": "^4.0.0-rc.7"
   },
   "dependencies": {
+    "chokidar": "^5.0.0",
     "schemastery": "^3.18.0",
     "yaml": "^2.4.2"
   },

packages/skill/skill-local/src/index.ts

@@ -10,9 +10,11 @@
  */
 
 import { access, readdir, readFile, stat } from 'node:fs/promises'
-import { dirname, join, resolve } from 'node:path'
+import { unwatchFile, watchFile, type Stats } from 'node:fs'
+import { dirname, isAbsolute, join, relative, resolve, sep } from 'node:path'
 import { homedir } from 'node:os'
 import type { Context } from 'cordis'
+import chokidar from 'chokidar'
 import z from 'schemastery'
 import type Schema from 'schemastery'
 import { parse as parseYaml } from 'yaml'
@@ -32,6 +34,9 @@ const PROJECT_AGENTS_RANK = 200
 const CUSTOM_RANK = 300
 const USER_DSH_RANK = 400
 const USER_AGENTS_RANK = 500
+const DEFAULT_WATCH_STABILITY_THRESHOLD_MS = 200
+const DEFAULT_WATCH_POLL_INTERVAL_MS = 100
+const DEFAULT_WATCH_MAX_PROJECTS = 128
 
 export const name = 'skill-local'
 export const inject = ['skills']
@@ -44,12 +49,30 @@ export interface Config {
   agentsHome?: string
   /** Additional skill roots scanned after project roots and before user roots. */
   customSkillDirs?: string[]
+  /** Whether host-local skill roots are watched for catalog changes. */
+  watch?: boolean
+  /** Whether Chokidar uses polling instead of native filesystem events. */
+  watchUsePolling?: boolean
+  /** Milliseconds a changed skill entry must remain stable before it is observed. */
+  watchStabilityThresholdMs?: number
+  /** Milliseconds between Chokidar stability or polling probes. */
+  watchPollIntervalMs?: number
+  /** Maximum distinct project roots whose skill directories remain watched. */
+  watchMaxProjects?: number
+  /** Whether watched symbolic links follow their target files. */
+  watchFollowSymlinks?: boolean
 }
 
 export const Config: Schema<Config> = z.object({
   dshHome: z.string(),
   agentsHome: z.string(),
   customSkillDirs: z.array(z.string()).default([]),
+  watch: z.boolean().default(true),
+  watchUsePolling: z.boolean().default(false),
+  watchStabilityThresholdMs: z.number().default(DEFAULT_WATCH_STABILITY_THRESHOLD_MS),
+  watchPollIntervalMs: z.number().default(DEFAULT_WATCH_POLL_INTERVAL_MS),
+  watchMaxProjects: z.number().default(DEFAULT_WATCH_MAX_PROJECTS),
+  watchFollowSymlinks: z.boolean().default(true),
 })
 
 interface SkillRoot {
@@ -57,6 +80,7 @@ interface SkillRoot {
   source: SkillSource
   rank: number
   skipSystem?: boolean
+  projectRoot?: string
 }
 
 interface SkillRootEntry {
@@ -79,10 +103,26 @@ interface LocalLocator {
   directory: string
 }
 
+interface ResolvedWatchConfig {
+  enabled: boolean
+  usePolling: boolean
+  stabilityThresholdMs: number
+  pollIntervalMs: number
+  maxProjects: number
+  followSymlinks: boolean
+}
+
 /** Register the local filesystem skill provider on `ctx.skills`. */
 export function apply(ctx: Context, config: Config = {}): void {
   const provider = new LocalSkillProvider(ctx, config)
   ctx.skills.registerProvider(provider)
+  ctx.effect(function* () {
+    yield async () => { await provider.dispose() }
+  }, 'skill-local watcher')
+  ctx.on('fs/observed', (target, _version, actor) => {
+    if (mutationToolName(actor) === undefined) return
+    provider.observeHostMutation(target.displayPath)
+  })
 }
 
 /** Provider that maps local project/user skill roots into `ctx.skills`. */
@@ -91,11 +131,13 @@ export class LocalSkillProvider implements SkillProvider {
   private readonly dshHome: string
   private readonly agentsHome: string
   private readonly customSkillDirs: string[]
+  private readonly watchManager: SkillWatchManager
 
   constructor(private readonly ctx: Context, config: Config = {}) {
     this.dshHome = resolveDshHome(config.dshHome)
     this.agentsHome = resolve(config.agentsHome ?? process.env.DSH_AGENTS_HOME ?? join(homedir(), '.agents'))
     this.customSkillDirs = (config.customSkillDirs ?? []).map(root => resolve(root))
+    this.watchManager = new SkillWatchManager(ctx, this, resolveWatchConfig(config))
   }
 
   /**
@@ -105,6 +147,7 @@ export class LocalSkillProvider implements SkillProvider {
    */
   async list(options: SkillLookupOptions): Promise<SkillCandidate[]> {
     const roots = await this.roots(options.cwd)
+    await this.watchManager.observeRoots(roots)
     const candidates: SkillCandidate[] = []
     for (const root of roots) {
       for (const skill of await discoverRoot(root, this.ctx)) {
@@ -138,13 +181,26 @@ export class LocalSkillProvider implements SkillProvider {
     }
   }
 
+  /**
+   * Invalidate this provider synchronously after a first-party filesystem mutation.
+   * @param path - host display path observed after a model-facing write or edit.
+   */
+  observeHostMutation(path: string): void {
+    this.watchManager.observeHostMutation(path)
+  }
+
+  /** Close every host watcher and contain late filesystem callbacks. */
+  async dispose(): Promise<void> {
+    await this.watchManager.dispose()
+  }
+
   private async roots(cwd: string | undefined): Promise<SkillRoot[]> {
     const roots: SkillRoot[] = []
     if (cwd !== undefined) {
       const projectRoot = await findProjectRoot(resolve(cwd), optionalFileSystem(this.ctx))
       roots.push(
-        { path: join(projectRoot, '.dsh/skills'), source: 'project-dsh', rank: PROJECT_DSH_RANK },
-        { path: join(projectRoot, '.agents/skills'), source: 'project-agents', rank: PROJECT_AGENTS_RANK },
+        { path: join(projectRoot, '.dsh/skills'), source: 'project-dsh', rank: PROJECT_DSH_RANK, projectRoot },
+        { path: join(projectRoot, '.agents/skills'), source: 'project-agents', rank: PROJECT_AGENTS_RANK, projectRoot },
       )
     }
     roots.push(
@@ -156,6 +212,405 @@ export class LocalSkillProvider implements SkillProvider {
   }
 }
 
+type SkillWatchEvent = 'add' | 'addDir' | 'change' | 'unlink' | 'unlinkDir'
+
+type RootWatchMode =
+  | { kind: 'root'; anchor: string }
+  | { kind: 'ancestor'; anchor: string; nextPath: string }
+
+interface RootWatchState {
+  root: SkillRoot
+  owners: Set<string>
+  watcher: WatchHandle | undefined
+  opening: Promise<void> | undefined
+  unhealthy: boolean
+}
+
+interface WatchHandle {
+  close(): Promise<void> | void
+}
+
+/** Owns bounded host watchers while discovery and reads remain on the filesystem service. */
+class SkillWatchManager {
+  private readonly roots = new Map<string, RootWatchState>()
+  private readonly projects = new Map<string, Set<string>>()
+  private closing = false
+  private invalidationQueued = false
+
+  constructor(
+    private readonly ctx: Context,
+    private readonly provider: SkillProvider,
+    private readonly config: ResolvedWatchConfig,
+  ) {}
+
+  async observeRoots(roots: readonly SkillRoot[]): Promise<void> {
+    if (this.closing) return
+    const projectRoots = new Map<string, SkillRoot[]>()
+    const pending: Promise<void>[] = []
+    for (const root of roots) {
+      if (root.projectRoot === undefined) {
+        pending.push(this.retainRoot(root, `shared:${root.path}`))
+        continue
+      }
+      const grouped = projectRoots.get(root.projectRoot) ?? []
+      grouped.push(root)
+      projectRoots.set(root.projectRoot, grouped)
+    }
+    for (const [projectRoot, grouped] of projectRoots) {
+      const owner = `project:${projectRoot}`
+      this.projects.delete(projectRoot)
+      const paths = new Set(grouped.map(root => root.path))
+      this.projects.set(projectRoot, paths)
+      for (const root of grouped) pending.push(this.retainRoot(root, owner))
+    }
+    let evictedProject = false
+    while (this.projects.size > this.config.maxProjects) {
+      const oldest = this.projects.entries().next()
+      /* v8 ignore next -- the loop condition proves one project exists. */
+      if (oldest.done) break
+      const [projectRoot, paths] = oldest.value
+      this.projects.delete(projectRoot)
+      const owner = `project:${projectRoot}`
+      for (const path of paths) pending.push(this.releaseRoot(path, owner))
+      evictedProject = true
+    }
+    await Promise.all(pending)
+    if (evictedProject) this.ctx.skills.invalidateProvider(this.provider)
+  }
+
+  observeHostMutation(path: string): void {
+    if (this.closing) return
+    const normalized = resolve(path)
+    if (![...this.roots.values()].some(state => isPotentialSkillPath(state.root, normalized))) return
+    this.ctx.skills.invalidateProvider(this.provider)
+  }
+
+  async dispose(): Promise<void> {
+    if (this.closing) return
+    this.closing = true
+    const states = [...this.roots.values()]
+    this.roots.clear()
+    this.projects.clear()
+    await Promise.all(states.map(async (state) => {
+      await settleWatcherOpening(state.opening)
+      const watcher = state.watcher
+      state.watcher = undefined
+      if (watcher !== undefined) await this.closeWatcher(watcher)
+    }))
+  }
+
+  private async retainRoot(root: SkillRoot, owner: string): Promise<void> {
+    let state = this.roots.get(root.path)
+    if (state === undefined) {
+      state = { root, owners: new Set(), watcher: undefined, opening: undefined, unhealthy: true }
+      this.roots.set(root.path, state)
+    }
+    state.owners.add(owner)
+    if (this.config.enabled) await this.ensureWatcher(state)
+  }
+
+  private async releaseRoot(path: string, owner: string): Promise<void> {
+    const state = this.roots.get(path)
+    /* v8 ignore next -- Concurrent cwd observations can evict the same shared root before this release settles. */
+    if (state === undefined) return
+    state.owners.delete(owner)
+    if (state.owners.size > 0) return
+    this.roots.delete(path)
+    await settleWatcherOpening(state.opening)
+    const watcher = state.watcher
+    state.watcher = undefined
+    if (watcher !== undefined) await this.closeWatcher(watcher)
+  }
+
+  private ensureWatcher(state: RootWatchState): Promise<void> {
+    if (this.closing || !this.config.enabled) return Promise.resolve()
+    if (state.watcher !== undefined && !state.unhealthy) return Promise.resolve()
+    if (state.opening !== undefined) return state.opening
+    const opening = this.replaceWatcher(state)
+    state.opening = opening
+    void opening.then(
+      () => {
+        state.opening = undefined
+      },
+      () => {
+        state.opening = undefined
+      },
+    )
+    return opening
+  }
+
+  private async replaceWatcher(state: RootWatchState): Promise<void> {
+    const previous = state.watcher
+    state.watcher = undefined
+    if (previous !== undefined) await this.closeWatcher(previous)
+    /* v8 ignore next -- Teardown can win while an unhealthy watcher is still closing. */
+    if (this.closing || state.owners.size === 0) return
+    try {
+      const watcher = await this.openStableWatcher(state)
+      /* v8 ignore next -- The loop returns no handle only when teardown wins between awaited probes. */
+      if (watcher === undefined) return
+      /* v8 ignore start -- Post-open teardown is timing-dependent; the disposal race has an explicit integration test. */
+      // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition -- teardown can race awaited watcher startup
+      if (this.closing || state.owners.size === 0) {
+        await this.closeWatcher(watcher)
+        return
+      }
+      /* v8 ignore stop */
+      state.watcher = watcher
+      state.unhealthy = false
+    } catch (error) {
+      state.unhealthy = true
+      this.ctx.logger.warn(`skill-local: failed to watch ${state.root.path}: ${errorMessage(error)}`)
+      throw error
+    }
+  }
+
+  private async openStableWatcher(state: RootWatchState): Promise<WatchHandle | undefined> {
+    while (!this.closing && state.owners.size > 0) {
+      const mode = await resolveRootWatchMode(state.root.path)
+      const watcher = mode.kind === 'ancestor'
+        ? this.openAncestorWatcher(state, mode)
+        : await this.openRootWatcher(state, mode)
+      const current = await resolveRootWatchMode(state.root.path)
+      /* v8 ignore else -- A host path transition between the two probes is timing-dependent. */
+      if (sameWatchMode(mode, current)) return watcher
+      /* v8 ignore next -- Covered by the same host path transition guard. */
+      await this.closeWatcher(watcher)
+    }
+    /* v8 ignore next -- The loop exits only when teardown wins between awaited probes. */
+    return undefined
+  }
+
+  private openAncestorWatcher(state: RootWatchState, mode: Extract<RootWatchMode, { kind: 'ancestor' }>): WatchHandle {
+    const listener = (_current: Stats, _previous: Stats): void => {
+      this.handleWatchEvent(state, mode, 'change', mode.nextPath)
+    }
+    watchFile(mode.nextPath, {
+      persistent: false,
+      interval: this.config.pollIntervalMs,
+    }, listener)
+    return {
+      close() {
+        unwatchFile(mode.nextPath, listener)
+      },
+    }
+  }
+
+  private async openRootWatcher(state: RootWatchState, mode: Extract<RootWatchMode, { kind: 'root' }>): Promise<WatchHandle> {
+    const watcher = chokidar.watch(mode.anchor, {
+      persistent: false,
+      ignoreInitial: true,
+      depth: 1,
+      followSymlinks: this.config.followSymlinks,
+      atomic: true,
+      awaitWriteFinish: {
+        stabilityThreshold: this.config.stabilityThresholdMs,
+        pollInterval: this.config.pollIntervalMs,
+      },
+      usePolling: this.config.usePolling,
+      interval: this.config.pollIntervalMs,
+    })
+    let ready = false
+    const readiness = Promise.withResolvers<undefined>()
+    const onError = (error: unknown): void => {
+      if (!ready) {
+        readiness.reject(error)
+        return
+      }
+      this.handleWatcherError(state, error)
+    }
+    watcher.on('error', onError)
+    watcher.once('ready', () => {
+      ready = true
+      readiness.resolve(undefined)
+    })
+    for (const event of ['add', 'addDir', 'change', 'unlink', 'unlinkDir'] as const) {
+      watcher.on(event, (path) => { this.handleWatchEvent(state, mode, event, path) })
+    }
+    try {
+      await readiness.promise
+    } catch (error) {
+      await this.closeWatcher(watcher)
+      throw error
+    }
+    return watcher
+  }
+
+  private handleWatchEvent(
+    state: RootWatchState,
+    mode: RootWatchMode,
+    event: SkillWatchEvent,
+    path: string,
+  ): void {
+    if (this.closing || !isRelevantWatchEvent(state.root, mode, event, resolve(path))) return
+    this.queueInvalidation()
+    if (mode.kind === 'ancestor' || (resolve(path) === state.root.path && event === 'unlinkDir')) {
+      state.unhealthy = true
+      this.scheduleRewatch(state)
+    }
+  }
+
+  private handleWatcherError(state: RootWatchState, error: unknown): void {
+    if (this.closing) return
+    this.ctx.logger.warn(`skill-local: watcher for ${state.root.path} failed: ${errorMessage(error)}`)
+    state.unhealthy = true
+    this.queueInvalidation()
+    this.scheduleRewatch(state)
+  }
+
+  private scheduleRewatch(state: RootWatchState): void {
+    const currentOpening = state.opening ?? Promise.resolve()
+    void (async () => {
+      await settleWatcherOpening(currentOpening)
+      try {
+        await this.ensureWatcher(state)
+      } catch {
+        // Watch startup logged the retry failure; the next incomplete discovery retries it again.
+        return
+      }
+      this.queueInvalidation()
+    })()
+  }
+
+  private queueInvalidation(): void {
+    if (this.closing || this.invalidationQueued) return
+    this.invalidationQueued = true
+    queueMicrotask(() => {
+      this.invalidationQueued = false
+      if (this.closing) return
+      this.ctx.skills.invalidateProvider(this.provider)
+    })
+  }
+
+  private async closeWatcher(watcher: WatchHandle): Promise<void> {
+    try {
+      await watcher.close()
+    } catch (error) {
+      this.ctx.logger.warn(`skill-local: failed to close watcher: ${errorMessage(error)}`)
+    }
+  }
+}
+
+async function settleWatcherOpening(opening: Promise<void> | undefined): Promise<void> {
+  if (opening === undefined) return
+  try {
+    await opening
+  } catch {
+    // Watch startup already logged the underlying failure; teardown only contains it.
+  }
+}
+
+function resolveWatchConfig(config: Config): ResolvedWatchConfig {
+  const stabilityThresholdMs = config.watchStabilityThresholdMs ?? DEFAULT_WATCH_STABILITY_THRESHOLD_MS
+  const pollIntervalMs = config.watchPollIntervalMs ?? DEFAULT_WATCH_POLL_INTERVAL_MS
+  const maxProjects = config.watchMaxProjects ?? DEFAULT_WATCH_MAX_PROJECTS
+  assertPositiveInteger('watchStabilityThresholdMs', stabilityThresholdMs)
+  assertPositiveInteger('watchPollIntervalMs', pollIntervalMs)
+  assertPositiveInteger('watchMaxProjects', maxProjects)
+  return {
+    enabled: config.watch ?? true,
+    usePolling: config.watchUsePolling ?? false,
+    stabilityThresholdMs,
+    pollIntervalMs,
+    maxProjects,
+    followSymlinks: config.watchFollowSymlinks ?? true,
+  }
+}
+
+async function resolveRootWatchMode(root: string): Promise<RootWatchMode> {
+  let candidate = root
+  while (true) {
+    try {
+      const info = await stat(candidate)
+      if (info.isDirectory()) {
+        if (candidate === root) return { kind: 'root', anchor: root }
+        const firstSegment = relative(candidate, root).split(sep)[0]
+        /* v8 ignore next -- candidate is a strict ancestor of root. */
+        if (firstSegment === undefined || firstSegment.length === 0) return { kind: 'root', anchor: root }
+        return { kind: 'ancestor', anchor: candidate, nextPath: join(candidate, firstSegment) }
+      }
+    } catch (error) {
+      /* v8 ignore next -- Non-absence stat failures are platform/permission-specific and propagate as incomplete discovery. */
+      if (!isAbsentPathError(error)) throw error
+    }
+    const parent = dirname(candidate)
+    /* v8 ignore next -- Traversal reaches the existing filesystem root before this fallback. */
+    if (parent === candidate) return { kind: 'ancestor', anchor: candidate, nextPath: root }
+    candidate = parent
+  }
+}
+
+function sameWatchMode(left: RootWatchMode, right: RootWatchMode): boolean {
+  return left.kind === right.kind
+    && left.anchor === right.anchor
+    && (left.kind === 'root' || (right.kind === 'ancestor' && left.nextPath === right.nextPath))
+}
+
+function isRelevantWatchEvent(
+  root: SkillRoot,
+  mode: RootWatchMode,
+  event: SkillWatchEvent,
+  path: string,
+): boolean {
+  if (mode.kind === 'ancestor') {
+    return path === mode.nextPath
+  }
+  const segments = containedSegments(root.path, path)
+  if (segments === undefined) return false
+  if (segments.length === 0) return event === 'addDir' || event === 'unlinkDir'
+  if (root.skipSystem === true && segments[0] === '.system') return false
+  if (segments.length === 1) {
+    if (event === 'addDir' || event === 'unlinkDir') return true
+    return segments[0]?.endsWith('.md') === true
+  }
+  return segments.length === 2
+    && segments[1] === 'SKILL.md'
+    && event !== 'addDir'
+    && event !== 'unlinkDir'
+}
+
+function isPotentialSkillPath(root: SkillRoot, path: string): boolean {
+  const segments = containedSegments(root.path, path)
+  if (segments === undefined || segments.length === 0 || segments.length > 2) return false
+  if (root.skipSystem === true && segments[0] === '.system') return false
+  return segments.length === 1
+    ? segments[0]?.endsWith('.md') === true
+    : segments[1] === 'SKILL.md'
+}
+
+function containedSegments(root: string, path: string): string[] | undefined {
+  const child = relative(root, path)
+  if (child.length === 0) return []
+  if (child === '..' || child.startsWith(`..${sep}`) || isAbsolute(child)) return undefined
+  return child.split(sep)
+}
+
+function mutationToolName(actor: object | undefined): 'edit' | 'write' | undefined {
+  if (actor === undefined || !('name' in actor)) return undefined
+  const value = actor.name
+  return value === 'edit' || value === 'write' ? value : undefined
+}
+
+function assertPositiveInteger(field: string, value: number): void {
+  if (!Number.isInteger(value) || value < 1) {
+    throw new TypeError(`skill-local: ${field} must be a positive integer`)
+  }
+}
+
+function isAbsentPathError(error: unknown): boolean {
+  return hasErrorCode(error, 'ENOENT') || hasErrorCode(error, 'ENOTDIR')
+}
+
+function isAbsentSkillPathError(error: unknown): boolean {
+  return isAbsentPathError(error)
+    || hasErrorCode(error, 'FS_NOT_FOUND')
+    || hasErrorCode(error, 'FS_NOT_DIRECTORY')
+}
+
+function hasErrorCode(error: unknown, code: string): boolean {
+  return typeof error === 'object' && error !== null && 'code' in error && error.code === code
+}
+
 async function discoverRoot(root: SkillRoot, ctx: Context): Promise<SkillCandidate[]> {
   const skills: SkillCandidate[] = []
   const entries = await listSkillRootEntries(root, ctx)
@@ -193,9 +648,12 @@ async function listSkillRootEntries(root: SkillRoot, ctx: Context): Promise<Skil
 }
 
 async function listSkillRootEntriesFromFileSystem(root: SkillRoot, fs: FileSystem): Promise<SkillRootEntry[]> {
-  // Skill roots are optional; an absent or unlistable root contributes no skills.
-  const entries = await fsListDir(fs, root.path).catch(() => undefined)
-  return entries === undefined ? [] : entries.map(entryFromFs)
+  try {
+    return (await fsListDir(fs, root.path)).map(entryFromFs)
+  } catch (error) {
+    if (isAbsentSkillPathError(error)) return []
+    throw error
+  }
 }
 
 async function fsListDir(fs: FileSystem, path: string): Promise<FsDirEntry[]> {
@@ -211,9 +669,11 @@ async function listSkillRootEntriesFromNode(root: SkillRoot, ctx: Context): Prom
   let entries
   try {
     entries = await readdir(root.path, { withFileTypes: true, encoding: 'utf8' })
-  } catch {
-    // Missing or unreadable local skill roots are expected in most deployments.
-    return []
+  } catch (error) {
+    /* v8 ignore else -- Native non-absence directory failures are provider-dependent; the ctx.fs path pins incomplete discovery. */
+    if (isAbsentSkillPathError(error)) return []
+    /* v8 ignore next -- Same native error branch as above. */
+    throw error
   }
 
   const result: SkillRootEntry[] = []
@@ -274,31 +734,39 @@ async function readSkillText(ctx: Context, path: string, signal?: AbortSignal):
   }
   try {
     return await readFile(path, { encoding: 'utf8', signal })
-  } catch {
+  } catch (error) {
     signal?.throwIfAborted()
-    return undefined
+    if (isAbsentSkillPathError(error)) return undefined
+    throw error
   }
 }
 
 async function readSkillTextFromFileSystem(ctx: Context, fs: FileSystem, path: string, signal?: AbortSignal): Promise<string | undefined> {
   // A missing or temporarily inaccessible skill file is not fatal to discovery.
   signal?.throwIfAborted()
-  const target = await fs.resolve(path).catch(() => undefined)
+  let target
+  try {
+    target = await fs.resolve(path)
+  } catch (error) {
+    if (isAbsentSkillPathError(error)) return undefined
+    throw error
+  }
   signal?.throwIfAborted()
-  if (target === undefined) return undefined
   let info
   try {
     info = await fs.stat(target, signal)
   } catch (error) {
     signal?.throwIfAborted()
-    ctx.logger.warn(`skill file ${path} ignored: failed to stat through filesystem service: ${errorMessage(error)}`)
-    return undefined
+    if (isAbsentSkillPathError(error)) return undefined
+    throw error
   }
   if (info === undefined || info.type !== 'file') return undefined
   try {
     return await fs.readText(target, signal)
   } catch (error) {
     signal?.throwIfAborted()
+    if (isAbsentSkillPathError(error)) return undefined
+    if (!hasErrorCode(error, 'FS_NOT_TEXT')) throw error
     ctx.logger.warn(`skill file ${path} ignored: ${fsReadErrorMessage(target, error)}`)
     return undefined
   }

packages/skill/skill-local/tests/skill-local-watcher.spec.ts

@@ -0,0 +1,220 @@
+import { EventEmitter } from 'node:events'
+import { mkdir, writeFile } from 'node:fs/promises'
+import { join } from 'node:path'
+import { tmpdir } from 'node:os'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { Context } from 'cordis'
+import SkillService from '@deepseek-ai/dsh-skill'
+
+interface FakeWatcherControl {
+  emitter: EventEmitter
+  closeCalls: number
+  options: Record<string, unknown>
+}
+
+const watcherHarness = vi.hoisted(() => ({
+  watchers: [] as FakeWatcherControl[],
+  startupErrors: [] as Error[],
+  closeErrors: 0,
+  deferredReady: 0,
+}))
+
+vi.mock('chokidar', () => ({
+  default: {
+    watch(_path: unknown, options: Record<string, unknown>) {
+      const emitter = new EventEmitter() as EventEmitter & { close(): Promise<void> }
+      const control: FakeWatcherControl = { emitter, closeCalls: 0, options }
+      emitter.close = async () => {
+        control.closeCalls += 1
+        if (watcherHarness.closeErrors > 0) {
+          watcherHarness.closeErrors -= 1
+          throw new Error('close failed')
+        }
+      }
+      watcherHarness.watchers.push(control)
+      queueMicrotask(() => {
+        if (watcherHarness.deferredReady > 0) {
+          watcherHarness.deferredReady -= 1
+          return
+        }
+        const error = watcherHarness.startupErrors.shift()
+        if (error === undefined) emitter.emit('ready')
+        else emitter.emit('error', error)
+      })
+      return emitter
+    },
+  },
+}))
+
+const SkillLocal = await import('../src/index.ts')
+
+async function tempDir(name: string): Promise<string> {
+  return await import('node:fs/promises').then(fs => fs.mkdtemp(join(tmpdir(), `dsh-${name}-`)))
+}
+
+async function writeSkill(root: string, name: string): Promise<void> {
+  const directory = join(root, name)
+  await mkdir(directory, { recursive: true })
+  await writeFile(join(directory, 'SKILL.md'), `---\nname: ${name}\ndescription: ${name}\n---\n\nBody.\n`)
+}
+
+async function settle(): Promise<void> {
+  await new Promise(resolve => setTimeout(resolve, 0))
+}
+
+beforeEach(() => {
+  watcherHarness.watchers.length = 0
+  watcherHarness.startupErrors.length = 0
+  watcherHarness.closeErrors = 0
+  watcherHarness.deferredReady = 0
+})
+
+describe('skill-local watcher failures', () => {
+  it('marks a startup failure incomplete and retries discovery without caching it', async () => {
+    const home = await tempDir('skill-watch-start-error')
+    const root = join(home, '.dsh/skills')
+    await writeSkill(root, 'retry-skill')
+    watcherHarness.startupErrors.push(new Error('watch failed'))
+    watcherHarness.closeErrors = 1
+    const ctx = new Context()
+    await ctx.plugin(SkillService)
+    const fiber = await ctx.plugin(SkillLocal, {
+      dshHome: join(home, '.dsh'),
+      agentsHome: join(home, '.agents'),
+      watch: true,
+      watchUsePolling: true,
+      watchFollowSymlinks: false,
+      watchPollIntervalMs: 10,
+      watchStabilityThresholdMs: 20,
+    })
+
+    expect(await ctx.skills.snapshot()).toEqual({ skills: [], complete: false })
+    expect(await ctx.skills.snapshot()).toMatchObject({
+      skills: [{ name: 'retry-skill' }],
+      complete: true,
+    })
+    expect(watcherHarness.watchers).toHaveLength(2)
+    expect(watcherHarness.watchers[1]?.options).toMatchObject({
+      atomic: true,
+      depth: 1,
+      followSymlinks: false,
+      usePolling: true,
+      interval: 10,
+      awaitWriteFinish: {
+        stabilityThreshold: 20,
+        pollInterval: 10,
+      },
+    })
+
+    await fiber.dispose()
+  })
+
+  it('filters events, coalesces invalidation, recovers runtime errors, and contains late callbacks', async () => {
+    const home = await tempDir('skill-watch-runtime-error')
+    const root = join(home, '.dsh/skills')
+    await writeSkill(root, 'watched-skill')
+    const ctx = new Context()
+    await ctx.plugin(SkillService)
+    const fiber = await ctx.plugin(SkillLocal, {
+      dshHome: join(home, '.dsh'),
+      agentsHome: join(home, '.agents'),
+      watch: true,
+      watchPollIntervalMs: 10,
+      watchStabilityThresholdMs: 20,
+    })
+    expect((await ctx.skills.list()).map(skill => skill.name)).toEqual(['watched-skill'])
+    const invalidateProvider = ctx.skills.invalidateProvider.bind(ctx.skills)
+    let invalidations = 0
+    ctx.skills.invalidateProvider = (provider) => {
+      invalidations += 1
+      invalidateProvider(provider)
+    }
+    const first = watcherHarness.watchers[0]
+    if (first === undefined) throw new Error('expected a root watcher')
+
+    first.emitter.emit('change', join(root, 'notes.txt'))
+    first.emitter.emit('change', join(home, 'outside.md'))
+    first.emitter.emit('change', join(root, 'watched-skill/references.md'))
+    first.emitter.emit('change', join(root, '.system/SKILL.md'))
+    await settle()
+    expect(invalidations).toBe(0)
+
+    first.emitter.emit('change', join(root, 'watched-skill/SKILL.md'))
+    first.emitter.emit('change', join(root, 'watched-skill/SKILL.md'))
+    await settle()
+    expect(invalidations).toBe(1)
+
+    watcherHarness.closeErrors = 1
+    watcherHarness.startupErrors.push(new Error('runtime rewatch failed'))
+    first.emitter.emit('error', new Error('runtime watch failed'))
+    await settle()
+    await settle()
+    expect(watcherHarness.watchers.length).toBeGreaterThanOrEqual(2)
+    expect(invalidations).toBeGreaterThanOrEqual(2)
+    expect(await ctx.skills.snapshot()).toMatchObject({
+      skills: [{ name: 'watched-skill' }],
+      complete: true,
+    })
+
+    await fiber.dispose()
+    first.emitter.emit('change', join(root, 'watched-skill/SKILL.md'))
+    first.emitter.emit('error', new Error('late error'))
+    await settle()
+  })
+
+  it('settles an opening watcher when plugin disposal races its ready event', async () => {
+    const home = await tempDir('skill-watch-opening-dispose')
+    const root = join(home, '.dsh/skills')
+    await writeSkill(root, 'racing-skill')
+    watcherHarness.deferredReady = 1
+    const ctx = new Context()
+    await ctx.plugin(SkillService)
+    const provider = new SkillLocal.LocalSkillProvider(ctx, {
+      dshHome: join(home, '.dsh'),
+      agentsHome: join(home, '.agents'),
+      watch: true,
+      watchPollIntervalMs: 10,
+      watchStabilityThresholdMs: 20,
+    })
+    ctx.skills.registerProvider(provider)
+
+    const discovery = provider.list({})
+    await settle()
+    const first = watcherHarness.watchers[0]
+    if (first === undefined) throw new Error('expected an opening root watcher')
+    first.emitter.emit('unlinkDir', root)
+    const disposal = provider.dispose()
+    first.emitter.emit('ready')
+
+    await Promise.all([discovery, disposal])
+    await settle()
+    expect(first.closeCalls).toBeGreaterThan(0)
+  })
+
+  it('contains an opening watcher rejection during provider teardown', async () => {
+    const home = await tempDir('skill-watch-opening-reject')
+    const root = join(home, '.dsh/skills')
+    await writeSkill(root, 'rejected-skill')
+    watcherHarness.deferredReady = 1
+    const ctx = new Context()
+    await ctx.plugin(SkillService)
+    const provider = new SkillLocal.LocalSkillProvider(ctx, {
+      dshHome: join(home, '.dsh'),
+      agentsHome: join(home, '.agents'),
+      watch: true,
+      watchPollIntervalMs: 10,
+      watchStabilityThresholdMs: 20,
+    })
+    ctx.skills.registerProvider(provider)
+
+    const discovery = provider.list({})
+    await settle()
+    const first = watcherHarness.watchers[0]
+    if (first === undefined) throw new Error('expected an opening root watcher')
+    const disposal = provider.dispose()
+    first.emitter.emit('error', new Error('opening failed during disposal'))
+
+    await expect(discovery).rejects.toThrow('opening failed during disposal')
+    await disposal
+  })
+})

packages/skill/skill-local/tests/skill-local.spec.ts

@@ -1,10 +1,10 @@
 import { describe, expect, it } from 'vitest'
-import { mkdir, readdir, readFile, stat, symlink, writeFile } from 'node:fs/promises'
+import { mkdir, readdir, readFile, rename, rm, stat, symlink, writeFile } from 'node:fs/promises'
 import { dirname, join } from 'node:path'
 import { tmpdir } from 'node:os'
 import { Context } from 'cordis'
 import SkillService from '@deepseek-ai/dsh-skill'
-import { FileSystem, FsVersion, type FsDirEntry, type FsEditOutcome, type FsEditRequest, type FsInfo, type FsPathInfo, type FsTarget, type FsWriteOutcome } from '@deepseek-ai/dsh-fs'
+import { FileSystem, FsError, FsVersion, type FsDirEntry, type FsEditOutcome, type FsEditRequest, type FsInfo, type FsPathInfo, type FsTarget, type FsWriteOutcome } from '@deepseek-ai/dsh-fs'
 import * as SkillLocal from '../src/index.ts'
 
 async function tempDir(name: string): Promise<string> {
@@ -26,19 +26,26 @@ class TestFileSystem extends FileSystem {
   listDirCalls = 0
   failResolvePaths = new Set<string>()
   failStatPaths = new Set<string>()
+  failListDirPaths = new Set<string>()
+  errorResolvePaths = new Set<string>()
+  errorStatPaths = new Set<string>()
+  errorReadPaths = new Set<string>()
+  missingReadPaths = new Set<string>()
   statOverrides = new Map<string, FsInfo | undefined>()
   statSignals: Array<AbortSignal | undefined> = []
   readTextSignals: Array<AbortSignal | undefined> = []
   readTextOverride?: (target: FsTarget, signal?: AbortSignal) => Promise<string>
 
   override async resolve(path: string): Promise<FsTarget> {
-    if (this.failResolvePaths.has(path)) throw new Error('resolve failed')
+    if (this.failResolvePaths.has(path)) throw new FsError('resolve failed', 'FS_NOT_FOUND')
+    if (this.errorResolvePaths.has(path)) throw new Error('resolve temporarily failed')
     return { targetKey: path as never, displayPath: path }
   }
 
   override async stat(target: FsTarget, signal?: AbortSignal): Promise<FsInfo | undefined> {
     this.statSignals.push(signal)
-    if (this.failStatPaths.has(target.displayPath)) throw new Error('stat failed')
+    if (this.failStatPaths.has(target.displayPath)) throw new FsError('stat failed', 'FS_NOT_FOUND')
+    if (this.errorStatPaths.has(target.displayPath)) throw new Error('stat temporarily failed')
     if (this.statOverrides.has(target.displayPath)) return this.statOverrides.get(target.displayPath)
     try {
       const fs = await import('node:fs/promises')
@@ -70,8 +77,10 @@ class TestFileSystem extends FileSystem {
   override async readText(target: FsTarget, signal?: AbortSignal): Promise<string> {
     this.readTextSignals.push(signal)
     if (this.readTextOverride !== undefined) return await this.readTextOverride(target, signal)
+    if (this.missingReadPaths.has(target.displayPath)) throw new FsError('read failed', 'FS_NOT_FOUND')
+    if (this.errorReadPaths.has(target.displayPath)) throw new Error('read temporarily failed')
     const text = await readFile(target.displayPath, 'utf8')
-    if (text.includes('\uFFFD')) throw new Error('not text')
+    if (text.includes('\uFFFD')) throw new FsError('not text', 'FS_NOT_TEXT')
     return text
   }
 
@@ -81,6 +90,7 @@ class TestFileSystem extends FileSystem {
 
   override async listDir(target: FsTarget): Promise<FsDirEntry[]> {
     this.listDirCalls += 1
+    if (this.failListDirPaths.has(target.displayPath)) throw new Error('list temporarily failed')
     const entries = await readdir(target.displayPath, { withFileTypes: true, encoding: 'utf8' })
     const result: FsDirEntry[] = []
     for (const entry of entries.sort((left, right) => left.name.localeCompare(right.name))) {
@@ -122,11 +132,22 @@ async function setupLocal(home: string, config: Partial<SkillLocal.Config> = {})
   await ctx.plugin(SkillLocal, {
     dshHome: join(home, '.dsh'),
     agentsHome: join(home, '.agents'),
+    watch: false,
     ...config,
   })
   return ctx
 }
 
+async function waitFor<T>(read: () => Promise<T>, accept: (value: T) => boolean): Promise<T> {
+  const deadline = Date.now() + 5000
+  while (true) {
+    const value = await read()
+    if (accept(value)) return value
+    if (Date.now() >= deadline) throw new Error('timed out waiting for watcher state')
+    await new Promise(resolve => setTimeout(resolve, 20))
+  }
+}
+
 describe('dsh-skill-local plugin exports', () => {
   it('declares stable plugin metadata', () => {
     expect(SkillLocal.name).toBe('skill-local')
@@ -224,7 +245,7 @@ describe('LocalSkillProvider', () => {
     const listedBeforeDelete = await ctx.skills.list()
     const flatSummary = listedBeforeDelete.find(skill => skill.name === 'flat-skill')
     if (flatSummary === undefined) throw new Error('expected flat-skill')
-    await writeFile(join(root, 'flat-skill.md'), '')
+    await rm(join(root, 'flat-skill.md'))
 
     expect(listedBeforeDelete.map(skill => skill.name)).toEqual(['flat-skill', 'no-trailing-body', 'rich-skill'])
     expect(await ctx.skills.get('flat-skill')).toBeUndefined()
@@ -327,7 +348,7 @@ describe('LocalSkillProvider', () => {
       size: 0,
     })
     await ctx.plugin(SkillService)
-    await ctx.plugin(SkillLocal, { dshHome: join(home, '.dsh'), agentsHome: join(home, '.agents') })
+    await ctx.plugin(SkillLocal, { dshHome: join(home, '.dsh'), agentsHome: join(home, '.agents'), watch: false })
 
     expect((await ctx.skills.list({ cwd: nestedCwd })).map(skill => [skill.name, skill.source])).toEqual([
       ['backend-root', 'project-agents'],
@@ -337,6 +358,92 @@ describe('LocalSkillProvider', () => {
     expect(await ctx.skills.get('binary-skill')).toBeUndefined()
   })
 
+  it('reports transient root reads as incomplete without caching an empty catalog', async () => {
+    const home = await tempDir('skill-transient-root')
+    const root = join(home, '.agents/skills')
+    await writeSkill(root, 'stable-skill', 'Stable skill')
+    const ctx = new Context()
+    await ctx.plugin(TestFileSystem)
+    const fs = ctx.fs as TestFileSystem
+    await ctx.plugin(SkillService)
+    await ctx.plugin(SkillLocal, {
+      dshHome: join(home, '.dsh'),
+      agentsHome: join(home, '.agents'),
+      watch: false,
+    })
+
+    expect(await ctx.skills.snapshot()).toMatchObject({
+      skills: [{ name: 'stable-skill' }],
+      complete: true,
+    })
+    fs.failListDirPaths.add(root)
+    const path = join(root, 'stable-skill/SKILL.md')
+    ctx.emit(
+      'fs/observed',
+      { targetKey: path as never, displayPath: path },
+      FsVersion('failed-read'),
+      { name: 'edit' },
+    )
+    expect(await ctx.skills.snapshot()).toEqual({ skills: [], complete: false })
+
+    fs.failListDirPaths.clear()
+    expect(await ctx.skills.snapshot()).toMatchObject({
+      skills: [{ name: 'stable-skill' }],
+      complete: true,
+    })
+  })
+
+  it('distinguishes transient filesystem entry failures from confirmed disappearance', async () => {
+    const home = await tempDir('skill-transient-entry')
+    const root = join(home, '.agents/skills')
+    const path = join(root, 'stable-skill/SKILL.md')
+    await writeSkill(root, 'stable-skill', 'Stable skill')
+    const ctx = new Context()
+    await ctx.plugin(TestFileSystem)
+    const fs = ctx.fs as TestFileSystem
+    await ctx.plugin(SkillService)
+    await ctx.plugin(SkillLocal, {
+      dshHome: join(home, '.dsh'),
+      agentsHome: join(home, '.agents'),
+      watch: false,
+    })
+    const invalidate = (): void => {
+      ctx.emit(
+        'fs/observed',
+        { targetKey: path as never, displayPath: path },
+        FsVersion('entry-failure'),
+        { name: 'write' },
+      )
+    }
+
+    expect((await ctx.skills.snapshot()).complete).toBe(true)
+    for (const failures of [fs.errorResolvePaths, fs.errorStatPaths, fs.errorReadPaths]) {
+      failures.add(path)
+      invalidate()
+      expect((await ctx.skills.snapshot()).complete).toBe(false)
+      failures.clear()
+    }
+
+    fs.missingReadPaths.add(path)
+    invalidate()
+    expect(await ctx.skills.snapshot()).toEqual({ skills: [], complete: true })
+    fs.missingReadPaths.clear()
+    invalidate()
+    expect(await ctx.skills.snapshot()).toMatchObject({
+      skills: [{ name: 'stable-skill' }],
+      complete: true,
+    })
+  })
+
+  it('marks an unexpected native skill-file read failure incomplete', async () => {
+    const home = await tempDir('skill-native-read-failure')
+    const root = join(home, '.agents/skills')
+    await mkdir(join(root, 'broken-skill/SKILL.md'), { recursive: true })
+    const ctx = await setupLocal(home)
+
+    expect(await ctx.skills.snapshot()).toEqual({ skills: [], complete: false })
+  })
+
   it('forwards cancellation to filesystem reads while loading a skill', async () => {
     const home = await tempDir('skill-read-abort')
     await writeSkill(join(home, '.dsh/skills'), 'abortable-skill', 'Abortable skill')
@@ -345,7 +452,7 @@ describe('LocalSkillProvider', () => {
     await ctx.plugin(TestFileSystem)
     const fs = ctx.fs as TestFileSystem
     await ctx.plugin(SkillService)
-    await ctx.plugin(SkillLocal, { dshHome: join(home, '.dsh'), agentsHome: join(home, '.agents') })
+    await ctx.plugin(SkillLocal, { dshHome: join(home, '.dsh'), agentsHome: join(home, '.agents'), watch: false })
     expect((await ctx.skills.list()).map(skill => skill.name)).toEqual(['abortable-skill'])
 
     fs.statSignals = []
@@ -372,6 +479,219 @@ describe('LocalSkillProvider', () => {
     expect(fs.readTextSignals).toEqual([controller.signal])
   })
 
+  it('refreshes additions, metadata changes, deletions, and a recreated missing root', { timeout: 20000 }, async () => {
+    const home = await tempDir('skill-watch-home')
+    const agentsRoot = join(home, '.agents/skills')
+    const ctx = new Context()
+    await ctx.plugin(SkillService)
+    const fiber = await ctx.plugin(SkillLocal, {
+      dshHome: join(home, '.dsh'),
+      agentsHome: join(home, '.agents'),
+      watch: true,
+      watchStabilityThresholdMs: 20,
+      watchPollIntervalMs: 10,
+    })
+    try {
+      expect(await ctx.skills.list()).toEqual([])
+
+      await writeSkill(agentsRoot, 'watched-skill', 'First description', 'First body.')
+      const added = await waitFor(
+        async () => await ctx.skills.list(),
+        skills => skills.some(skill => skill.name === 'watched-skill'),
+      )
+      expect(added.find(skill => skill.name === 'watched-skill')?.description).toBe('First description')
+
+      await writeSkill(agentsRoot, 'watched-skill', 'Second description', 'Second body.')
+      const changed = await waitFor(
+        async () => await ctx.skills.list(),
+        skills => skills.find(skill => skill.name === 'watched-skill')?.description === 'Second description',
+      )
+      expect(changed).toHaveLength(1)
+      expect((await ctx.skills.get('watched-skill'))?.content).toBe('Second body.')
+
+      await writeFlatSkill(agentsRoot, 'flat-added', 'Flat added')
+      expect(await waitFor(
+        async () => (await ctx.skills.list()).map(skill => skill.name),
+        names => names.includes('flat-added'),
+      )).toEqual(['flat-added', 'watched-skill'])
+
+      await rename(join(agentsRoot, 'watched-skill'), join(agentsRoot, 'renamed-skill'))
+      await writeSkill(agentsRoot, 'renamed-skill', 'Renamed skill')
+      expect(await waitFor(
+        async () => (await ctx.skills.list()).map(skill => skill.name),
+        names => names.includes('renamed-skill') && !names.includes('watched-skill'),
+      )).toEqual(['flat-added', 'renamed-skill'])
+
+      await rm(join(agentsRoot, 'renamed-skill'), { recursive: true })
+      expect(await waitFor(
+        async () => (await ctx.skills.list()).map(skill => skill.name),
+        names => !names.includes('renamed-skill'),
+      )).toEqual(['flat-added'])
+
+      await rm(join(home, '.agents'), { recursive: true })
+      expect(await waitFor(
+        async () => await ctx.skills.list(),
+        skills => skills.length === 0,
+      )).toEqual([])
+
+      await writeSkill(agentsRoot, 'recreated-skill', 'Recreated')
+      expect(await waitFor(
+        async () => (await ctx.skills.list()).map(skill => skill.name),
+        names => names.includes('recreated-skill'),
+      )).toEqual(['recreated-skill'])
+    } finally {
+      await fiber.dispose()
+    }
+
+  })
+
+  it('uses fs/observed as a synchronous first-party invalidation path without a watcher', async () => {
+    const home = await tempDir('skill-observed-home')
+    const root = join(home, '.agents/skills')
+    const ctx = await setupLocal(home)
+    expect(await ctx.skills.list()).toEqual([])
+    const invalidateProvider = ctx.skills.invalidateProvider.bind(ctx.skills)
+    let invalidations = 0
+    ctx.skills.invalidateProvider = (provider) => {
+      invalidations += 1
+      invalidateProvider(provider)
+    }
+
+    await writeSkill(root, 'observed-skill', 'Observed skill')
+    const path = join(root, 'observed-skill/SKILL.md')
+    const emitObserved = (displayPath: string, actor?: object): void => {
+      ctx.emit(
+        'fs/observed',
+        { targetKey: displayPath as never, displayPath },
+        FsVersion('observed'),
+        actor,
+      )
+    }
+    emitObserved(path)
+    emitObserved(path, {})
+    emitObserved(path, { name: 'read' })
+    emitObserved(join(home, 'outside.md'), { name: 'write' })
+    emitObserved(root, { name: 'write' })
+    emitObserved(join(root, 'observed-skill/references/notes.md'), { name: 'write' })
+    emitObserved(join(home, '.dsh/skills/.system/SKILL.md'), { name: 'write' })
+    emitObserved(join(root, 'flat-skill.md'), { name: 'write' })
+    ctx.emit(
+      'fs/observed',
+      { targetKey: path as never, displayPath: path },
+      FsVersion('observed'),
+      { name: 'edit' },
+    )
+
+    expect(invalidations).toBe(2)
+    expect((await ctx.skills.list()).map(skill => skill.name)).toEqual(['observed-skill'])
+  })
+
+  it('bounds project watchers and re-observes an evicted project on its next lookup', async () => {
+    const home = await tempDir('skill-watch-lru-home')
+    const first = await tempDir('skill-watch-lru-first')
+    const second = await tempDir('skill-watch-lru-second')
+    await mkdir(join(first, '.git'), { recursive: true })
+    await mkdir(join(second, '.git'), { recursive: true })
+    await writeSkill(join(first, '.agents/skills'), 'first-project', 'First project')
+    await writeSkill(join(second, '.agents/skills'), 'second-project', 'Second project')
+    const ctx = new Context()
+    await ctx.plugin(SkillService)
+    const fiber = await ctx.plugin(SkillLocal, {
+      dshHome: join(home, '.dsh'),
+      agentsHome: join(home, '.agents'),
+      customSkillDirs: [join(first, '.agents/skills')],
+      watch: true,
+      watchMaxProjects: 1,
+      watchStabilityThresholdMs: 20,
+      watchPollIntervalMs: 10,
+    })
+    try {
+      expect((await ctx.skills.list({ cwd: first })).map(skill => skill.name)).toContain('first-project')
+      expect((await ctx.skills.list({ cwd: second })).map(skill => skill.name)).toContain('second-project')
+      await writeSkill(join(first, '.agents/skills'), 'first-project', 'First project refreshed')
+
+      expect((await ctx.skills.list({ cwd: first })).find(skill => skill.name === 'first-project')?.description)
+        .toBe('First project refreshed')
+    } finally {
+      await fiber.dispose()
+    }
+
+    const noWatch = new Context()
+    await noWatch.plugin(SkillService)
+    await noWatch.plugin(SkillLocal, {
+      dshHome: join(home, '.dsh'),
+      agentsHome: join(home, '.agents'),
+      watch: false,
+      watchMaxProjects: 1,
+    })
+    await noWatch.skills.list({ cwd: first })
+    await noWatch.skills.list({ cwd: second })
+  })
+
+  it('contains repeated disposal and late first-party observations', async () => {
+    const home = await tempDir('skill-watch-dispose')
+    const nonDirectoryRoot = join(home, 'not-a-directory')
+    await writeFile(nonDirectoryRoot, 'not a skill root')
+    await writeSkill(join(home, '.agents/skills'), 'disposed-skill', 'Disposed skill')
+    const ctx = new Context()
+    await ctx.plugin(SkillService)
+    const provider = new SkillLocal.LocalSkillProvider(ctx, {
+      dshHome: join(home, '.dsh'),
+      agentsHome: join(home, '.agents'),
+      customSkillDirs: [nonDirectoryRoot],
+      watch: true,
+      watchStabilityThresholdMs: 20,
+      watchPollIntervalMs: 10,
+    })
+    ctx.skills.registerProvider(provider)
+    expect((await provider.list({})).map(skill => skill.name)).toEqual(['disposed-skill'])
+
+    await provider.dispose()
+    await provider.dispose()
+    provider.observeHostMutation(join(home, '.agents/skills/disposed-skill/SKILL.md'))
+
+    expect((await provider.list({})).map(skill => skill.name)).toEqual(['disposed-skill'])
+  })
+
+  it('refreshes frontmatter through a followed skill symlink', { timeout: 10000 }, async () => {
+    const home = await tempDir('skill-watch-symlink-home')
+    const external = await tempDir('skill-watch-symlink-external')
+    const root = join(home, '.dsh/skills')
+    await writeSkill(external, 'linked-skill', 'First linked description')
+    await mkdir(root, { recursive: true })
+    await symlink(join(external, 'linked-skill'), join(root, 'linked-skill'))
+    const ctx = new Context()
+    await ctx.plugin(SkillService)
+    const fiber = await ctx.plugin(SkillLocal, {
+      dshHome: join(home, '.dsh'),
+      agentsHome: join(home, '.agents'),
+      watch: true,
+      watchFollowSymlinks: true,
+      watchStabilityThresholdMs: 20,
+      watchPollIntervalMs: 10,
+    })
+    try {
+      expect((await ctx.skills.list())[0]?.description).toBe('First linked description')
+      await writeSkill(external, 'linked-skill', 'Second linked description')
+      const refreshed = await waitFor(
+        async () => await ctx.skills.list(),
+        skills => skills[0]?.description === 'Second linked description',
+      )
+      expect(refreshed[0]?.name).toBe('linked-skill')
+    } finally {
+      await fiber.dispose()
+    }
+  })
+
+  it('validates watcher tunables at plugin load', async () => {
+    const ctx = new Context()
+    await ctx.plugin(SkillService)
+
+    await expect(ctx.plugin(SkillLocal, { watchMaxProjects: 0 })).rejects.toThrow('watchMaxProjects')
+    await expect(ctx.plugin(SkillLocal, { watchPollIntervalMs: 1.5 })).rejects.toThrow('watchPollIntervalMs')
+    await expect(ctx.plugin(SkillLocal, { watchStabilityThresholdMs: 0 })).rejects.toThrow('watchStabilityThresholdMs')
+  })
+
   it('uses default home root resolution without exposing builtin skills', async () => {
     const previousDshHome = process.env.DSH_HOME
     const previousAgentsHome = process.env.DSH_AGENTS_HOME
@@ -382,14 +702,14 @@ describe('LocalSkillProvider', () => {
       await writeSkill(join(envHome, '.dsh/skills'), 'env-skill', 'Env skill')
       const ctx = new Context()
       await ctx.plugin(SkillService)
-      await ctx.plugin(SkillLocal)
+      await ctx.plugin(SkillLocal, { watch: false })
       expect((await ctx.skills.list()).map(skill => skill.name)).toEqual(['env-skill'])
 
       process.env.DSH_HOME = join(envHome, 'empty-dsh')
       process.env.DSH_AGENTS_HOME = join(envHome, 'empty-agents')
       const empty = new Context()
       await empty.plugin(SkillService)
-      SkillLocal.apply(empty, {})
+      SkillLocal.apply(empty, { watch: false })
       expect(await empty.skills.list()).toEqual([])
 
       delete process.env.DSH_AGENTS_HOME