migrate: move flock and hash utilities to shared package (#22640)

2026-04-15 11:50:24 -04:00
parent f1751401aa
commit 4ae7c77f8a
23 changed files with 929 additions and 41 deletions
--- a/packages/shared/package.json
+++ b/packages/shared/package.json
@@ -5,7 +5,9 @@
  "type": "module",
  "license": "MIT",
  "private": true,
-  "scripts": {},
+  "scripts": {
+    "test": "bun test"
+  },
  "bin": {
    "opencode": "./bin/opencode"
  },
@@ -14,7 +16,8 @@
  },
  "imports": {},
  "devDependencies": {
-    "@types/semver": "catalog:"
+    "@types/semver": "catalog:",
+    "@types/bun": "catalog:"
  },
  "dependencies": {
    "@effect/platform-node": "catalog:",
@@ -23,6 +26,7 @@
    "mime-types": "3.0.2",
    "minimatch": "10.2.5",
    "semver": "catalog:",
+    "xdg-basedir": "5.1.0",
    "zod": "catalog:"
  },
  "overrides": {
--- a/packages/shared/src/global.ts
+++ b/packages/shared/src/global.ts
@@ -0,0 +1,42 @@
+import path from "path"
+import { xdgData, xdgCache, xdgConfig, xdgState } from "xdg-basedir"
+import os from "os"
+import { Context, Effect, Layer } from "effect"
+
+export namespace Global {
+  export class Service extends Context.Service<Service, Interface>()("@opencode/Global") {}
+
+  export interface Interface {
+    readonly home: string
+    readonly data: string
+    readonly cache: string
+    readonly config: string
+    readonly state: string
+    readonly bin: string
+    readonly log: string
+  }
+
+  export const layer = Layer.effect(
+    Service,
+    Effect.gen(function* () {
+      const app = "opencode"
+      const home = process.env.OPENCODE_TEST_HOME ?? os.homedir()
+      const data = path.join(xdgData!, app)
+      const cache = path.join(xdgCache!, app)
+      const cfg = path.join(xdgConfig!, app)
+      const state = path.join(xdgState!, app)
+      const bin = path.join(cache, "bin")
+      const log = path.join(data, "log")
+
+      return Service.of({
+        home,
+        data,
+        cache,
+        config: cfg,
+        state,
+        bin,
+        log,
+      })
+    }),
+  )
+}
--- a/packages/shared/src/npm.ts
+++ b/packages/shared/src/npm.ts
@@ -0,0 +1,247 @@
+import path from "path"
+import semver from "semver"
+import { Arborist } from "@npmcli/arborist"
+import { Effect, Schema, Context, Layer, Option, FileSystem } from "effect"
+import { NodeFileSystem } from "@effect/platform-node"
+import { AppFileSystem } from "./filesystem"
+import { Global } from "./global"
+import { Flock } from "./util/flock"
+
+export namespace Npm {
+  export class InstallFailedError extends Schema.TaggedErrorClass<InstallFailedError>()("NpmInstallFailedError", {
+    pkg: Schema.String,
+    cause: Schema.optional(Schema.Defect),
+  }) {}
+
+  export interface EntryPoint {
+    readonly directory: string
+    readonly entrypoint: Option.Option<string>
+  }
+
+  export interface Interface {
+    readonly add: (pkg: string) => Effect.Effect<EntryPoint, InstallFailedError>
+    readonly install: (dir: string) => Effect.Effect<void>
+    readonly outdated: (pkg: string, cachedVersion: string) => Effect.Effect<boolean>
+    readonly which: (pkg: string) => Effect.Effect<Option.Option<string>>
+  }
+
+  export class Service extends Context.Service<Service, Interface>()("@opencode/Npm") {}
+
+  const illegal = process.platform === "win32" ? new Set(["<", ">", ":", '"', "|", "?", "*"]) : undefined
+
+  export function sanitize(pkg: string) {
+    if (!illegal) return pkg
+    return Array.from(pkg, (char) => (illegal.has(char) || char.charCodeAt(0) < 32 ? "_" : char)).join("")
+  }
+
+  const resolveEntryPoint = (name: string, dir: string): EntryPoint => {
+    let entrypoint: Option.Option<string>
+    try {
+      const resolved = typeof Bun !== "undefined" ? import.meta.resolve(name, dir) : import.meta.resolve(dir)
+      entrypoint = Option.some(resolved)
+    } catch {
+      entrypoint = Option.none()
+    }
+    return {
+      directory: dir,
+      entrypoint,
+    }
+  }
+
+  interface ArboristNode {
+    name: string
+    path: string
+  }
+
+  interface ArboristTree {
+    edgesOut: Map<string, { to?: ArboristNode }>
+  }
+  export const layer = Layer.effect(
+    Service,
+    Effect.gen(function* () {
+      const afs = yield* AppFileSystem.Service
+      const global = yield* Global.Service
+      const fs = yield* FileSystem.FileSystem
+      const directory = (pkg: string) => path.join(global.cache, "packages", sanitize(pkg))
+
+      const outdated = Effect.fn("Npm.outdated")(function* (pkg: string, cachedVersion: string) {
+        const response = yield* Effect.tryPromise({
+          try: () => fetch(`https://registry.npmjs.org/${pkg}`),
+          catch: () => undefined,
+        }).pipe(Effect.orElseSucceed(() => undefined))
+
+        if (!response || !response.ok) {
+          return false
+        }
+
+        const data = yield* Effect.tryPromise({
+          try: () => response.json() as Promise<{ "dist-tags"?: { latest?: string } }>,
+          catch: () => undefined,
+        }).pipe(Effect.orElseSucceed(() => undefined))
+
+        const latestVersion = data?.["dist-tags"]?.latest
+        if (!latestVersion) {
+          return false
+        }
+
+        const range = /[\s^~*xX<>|=]/.test(cachedVersion)
+        if (range) return !semver.satisfies(latestVersion, cachedVersion)
+
+        return semver.lt(cachedVersion, latestVersion)
+      })
+
+      const add = Effect.fn("Npm.add")(function* (pkg: string) {
+        const dir = directory(pkg)
+        yield* Flock.effect(`npm-install:${dir}`)
+
+        const arborist = new Arborist({
+          path: dir,
+          binLinks: true,
+          progress: false,
+          savePrefix: "",
+          ignoreScripts: true,
+        })
+
+        const tree = yield* Effect.tryPromise({
+          try: () => arborist.loadVirtual().catch(() => undefined),
+          catch: () => undefined,
+        }).pipe(Effect.orElseSucceed(() => undefined)) as Effect.Effect<ArboristTree | undefined>
+
+        if (tree) {
+          const first = tree.edgesOut.values().next().value?.to
+          if (first) {
+            return resolveEntryPoint(first.name, first.path)
+          }
+        }
+
+        const result = yield* Effect.tryPromise({
+          try: () =>
+            arborist.reify({
+              add: [pkg],
+              save: true,
+              saveType: "prod",
+            }),
+          catch: (cause) => new InstallFailedError({ pkg, cause }),
+        }) as Effect.Effect<ArboristTree, InstallFailedError>
+
+        const first = result.edgesOut.values().next().value?.to
+        if (!first) {
+          return yield* new InstallFailedError({ pkg })
+        }
+
+        return resolveEntryPoint(first.name, first.path)
+      }, Effect.scoped)
+
+      const install = Effect.fn("Npm.install")(function* (dir: string) {
+        yield* Flock.effect(`npm-install:${dir}`)
+
+        const reify = Effect.fnUntraced(function* () {
+          const arb = new Arborist({
+            path: dir,
+            binLinks: true,
+            progress: false,
+            savePrefix: "",
+            ignoreScripts: true,
+          })
+          yield* Effect.tryPromise({
+            try: () => arb.reify().catch(() => {}),
+            catch: () => {},
+          }).pipe(Effect.orElseSucceed(() => {}))
+        })
+
+        const nodeModulesExists = yield* afs.existsSafe(path.join(dir, "node_modules"))
+        if (!nodeModulesExists) {
+          yield* reify()
+          return
+        }
+
+        const pkg = yield* afs.readJson(path.join(dir, "package.json")).pipe(Effect.orElseSucceed(() => ({})))
+        const lock = yield* afs.readJson(path.join(dir, "package-lock.json")).pipe(Effect.orElseSucceed(() => ({})))
+
+        const pkgAny = pkg as any
+        const lockAny = lock as any
+
+        const declared = new Set([
+          ...Object.keys(pkgAny?.dependencies || {}),
+          ...Object.keys(pkgAny?.devDependencies || {}),
+          ...Object.keys(pkgAny?.peerDependencies || {}),
+          ...Object.keys(pkgAny?.optionalDependencies || {}),
+        ])
+
+        const root = lockAny?.packages?.[""] || {}
+        const locked = new Set([
+          ...Object.keys(root?.dependencies || {}),
+          ...Object.keys(root?.devDependencies || {}),
+          ...Object.keys(root?.peerDependencies || {}),
+          ...Object.keys(root?.optionalDependencies || {}),
+        ])
+
+        for (const name of declared) {
+          if (!locked.has(name)) {
+            yield* reify()
+            return
+          }
+        }
+      }, Effect.scoped)
+
+      const which = Effect.fn("Npm.which")(function* (pkg: string) {
+        const dir = directory(pkg)
+        const binDir = path.join(dir, "node_modules", ".bin")
+
+        const pick = Effect.fnUntraced(function* () {
+          const files = yield* fs.readDirectory(binDir).pipe(Effect.catch(() => Effect.succeed([] as string[])))
+
+          if (files.length === 0) return Option.none<string>()
+          if (files.length === 1) return Option.some(files[0])
+
+          const pkgJson = yield* afs.readJson(path.join(dir, "node_modules", pkg, "package.json")).pipe(Effect.option)
+
+          if (Option.isSome(pkgJson)) {
+            const parsed = pkgJson.value as { bin?: string | Record<string, string> }
+            if (parsed?.bin) {
+              const unscoped = pkg.startsWith("@") ? pkg.split("/")[1] : pkg
+              const bin = parsed.bin
+              if (typeof bin === "string") return Option.some(unscoped)
+              const keys = Object.keys(bin)
+              if (keys.length === 1) return Option.some(keys[0])
+              return bin[unscoped] ? Option.some(unscoped) : Option.some(keys[0])
+            }
+          }
+
+          return Option.some(files[0])
+        })
+
+        return yield* Effect.gen(function* () {
+          const bin = yield* pick()
+          if (Option.isSome(bin)) {
+            return Option.some(path.join(binDir, bin.value))
+          }
+
+          yield* fs.remove(path.join(dir, "package-lock.json")).pipe(Effect.orElseSucceed(() => {}))
+
+          yield* add(pkg)
+
+          const resolved = yield* pick()
+          if (Option.isNone(resolved)) return Option.none<string>()
+          return Option.some(path.join(binDir, resolved.value))
+        }).pipe(
+          Effect.scoped,
+          Effect.orElseSucceed(() => Option.none<string>()),
+        )
+      })
+
+      return Service.of({
+        add,
+        install,
+        outdated,
+        which,
+      })
+    }),
+  )
+
+  export const defaultLayer = layer.pipe(
+    Layer.provide(AppFileSystem.layer),
+    Layer.provide(Global.layer),
+    Layer.provide(NodeFileSystem.layer),
+  )
+}
--- a/packages/shared/src/types.d.ts
+++ b/packages/shared/src/types.d.ts
@@ -0,0 +1,44 @@
+declare module "@npmcli/arborist" {
+  export interface ArboristOptions {
+    path: string
+    binLinks?: boolean
+    progress?: boolean
+    savePrefix?: string
+    ignoreScripts?: boolean
+  }
+
+  export interface ArboristNode {
+    name: string
+    path: string
+  }
+
+  export interface ArboristEdge {
+    to?: ArboristNode
+  }
+
+  export interface ArboristTree {
+    edgesOut: Map<string, ArboristEdge>
+  }
+
+  export interface ReifyOptions {
+    add?: string[]
+    save?: boolean
+    saveType?: "prod" | "dev" | "optional" | "peer"
+  }
+
+  export class Arborist {
+    constructor(options: ArboristOptions)
+    loadVirtual(): Promise<ArboristTree | undefined>
+    reify(options?: ReifyOptions): Promise<ArboristTree>
+  }
+}
+
+declare var Bun:
+  | {
+      file(path: string): {
+        text(): Promise<string>
+        json(): Promise<unknown>
+      }
+      write(path: string, content: string | Uint8Array): Promise<void>
+    }
+  | undefined
--- a/packages/shared/src/util/flock.ts
+++ b/packages/shared/src/util/flock.ts
@@ -0,0 +1,354 @@
+import path from "path"
+import os from "os"
+import { randomBytes, randomUUID } from "crypto"
+import { mkdir, readFile, rm, stat, utimes, writeFile } from "fs/promises"
+import { Hash } from "./hash"
+import { Effect } from "effect"
+
+export type FlockGlobal = {
+  state: string
+}
+
+export namespace Flock {
+  let global: FlockGlobal | undefined
+
+  export function setGlobal(g: FlockGlobal) {
+    global = g
+  }
+
+  const root = () => {
+    if (!global) throw new Error("Flock global not set")
+    return path.join(global.state, "locks")
+  }
+
+  // Defaults for callers that do not provide timing options.
+  const defaultOpts = {
+    staleMs: 60_000,
+    timeoutMs: 5 * 60_000,
+    baseDelayMs: 100,
+    maxDelayMs: 2_000,
+  }
+
+  export interface WaitEvent {
+    key: string
+    attempt: number
+    delay: number
+    waited: number
+  }
+
+  export type Wait = (input: WaitEvent) => void | Promise<void>
+
+  export interface Options {
+    dir?: string
+    signal?: AbortSignal
+    staleMs?: number
+    timeoutMs?: number
+    baseDelayMs?: number
+    maxDelayMs?: number
+    onWait?: Wait
+  }
+
+  type Opts = {
+    staleMs: number
+    timeoutMs: number
+    baseDelayMs: number
+    maxDelayMs: number
+  }
+
+  type Owned = {
+    acquired: true
+    startHeartbeat: (intervalMs?: number) => void
+    release: () => Promise<void>
+  }
+
+  export interface Lease {
+    release: () => Promise<void>
+    [Symbol.asyncDispose]: () => Promise<void>
+  }
+
+  function code(err: unknown) {
+    if (typeof err !== "object" || err === null || !("code" in err)) return
+    const value = err.code
+    if (typeof value !== "string") return
+    return value
+  }
+
+  function sleep(ms: number, signal?: AbortSignal) {
+    return new Promise<void>((resolve, reject) => {
+      if (signal?.aborted) {
+        reject(signal.reason ?? new Error("Aborted"))
+        return
+      }
+
+      let timer: NodeJS.Timeout | undefined
+
+      const done = () => {
+        signal?.removeEventListener("abort", abort)
+        resolve()
+      }
+
+      const abort = () => {
+        if (timer) {
+          clearTimeout(timer)
+        }
+        signal?.removeEventListener("abort", abort)
+        reject(signal?.reason ?? new Error("Aborted"))
+      }
+
+      signal?.addEventListener("abort", abort, { once: true })
+      timer = setTimeout(done, ms)
+    })
+  }
+
+  function jitter(ms: number) {
+    const j = Math.floor(ms * 0.3)
+    const d = Math.floor(Math.random() * (2 * j + 1)) - j
+    return Math.max(0, ms + d)
+  }
+
+  function mono() {
+    return performance.now()
+  }
+
+  function wall() {
+    return performance.timeOrigin + mono()
+  }
+
+  async function stats(file: string) {
+    try {
+      return await stat(file)
+    } catch (err) {
+      const errCode = code(err)
+      if (errCode === "ENOENT" || errCode === "ENOTDIR") return
+      throw err
+    }
+  }
+
+  async function stale(lockDir: string, heartbeatPath: string, metaPath: string, staleMs: number) {
+    // Stale detection allows automatic recovery after crashed owners.
+    const now = wall()
+    const heartbeat = await stats(heartbeatPath)
+    if (heartbeat) {
+      return now - heartbeat.mtimeMs > staleMs
+    }
+
+    const meta = await stats(metaPath)
+    if (meta) {
+      return now - meta.mtimeMs > staleMs
+    }
+
+    const dir = await stats(lockDir)
+    if (!dir) {
+      return false
+    }
+
+    return now - dir.mtimeMs > staleMs
+  }
+
+  async function tryAcquireLockDir(lockDir: string, opts: Opts): Promise<Owned | { acquired: false }> {
+    const token = randomUUID?.() ?? randomBytes(16).toString("hex")
+    const metaPath = path.join(lockDir, "meta.json")
+    const heartbeatPath = path.join(lockDir, "heartbeat")
+
+    try {
+      await mkdir(lockDir, { mode: 0o700 })
+    } catch (err) {
+      if (code(err) !== "EEXIST") {
+        throw err
+      }
+
+      if (!(await stale(lockDir, heartbeatPath, metaPath, opts.staleMs))) {
+        return { acquired: false }
+      }
+
+      const breakerPath = lockDir + ".breaker"
+      try {
+        await mkdir(breakerPath, { mode: 0o700 })
+      } catch (claimErr) {
+        const errCode = code(claimErr)
+        if (errCode === "EEXIST") {
+          const breaker = await stats(breakerPath)
+          if (breaker && wall() - breaker.mtimeMs > opts.staleMs) {
+            await rm(breakerPath, { recursive: true, force: true }).catch(() => undefined)
+          }
+          return { acquired: false }
+        }
+
+        if (errCode === "ENOENT" || errCode === "ENOTDIR") {
+          return { acquired: false }
+        }
+
+        throw claimErr
+      }
+
+      try {
+        // Breaker ownership ensures only one contender performs stale cleanup.
+        if (!(await stale(lockDir, heartbeatPath, metaPath, opts.staleMs))) {
+          return { acquired: false }
+        }
+
+        await rm(lockDir, { recursive: true, force: true })
+
+        try {
+          await mkdir(lockDir, { mode: 0o700 })
+        } catch (retryErr) {
+          const errCode = code(retryErr)
+          if (errCode === "EEXIST" || errCode === "ENOTEMPTY") {
+            return { acquired: false }
+          }
+          throw retryErr
+        }
+      } finally {
+        await rm(breakerPath, { recursive: true, force: true }).catch(() => undefined)
+      }
+    }
+
+    const meta = {
+      token,
+      pid: process.pid,
+      hostname: os.hostname(),
+      createdAt: new Date().toISOString(),
+    }
+
+    await writeFile(heartbeatPath, "", { flag: "wx" }).catch(async () => {
+      await rm(lockDir, { recursive: true, force: true })
+      throw new Error("Lock acquired but heartbeat already existed (possible compromise).")
+    })
+
+    await writeFile(metaPath, JSON.stringify(meta, null, 2), { flag: "wx" }).catch(async () => {
+      await rm(lockDir, { recursive: true, force: true })
+      throw new Error("Lock acquired but meta.json already existed (possible compromise).")
+    })
+
+    let timer: NodeJS.Timeout | undefined
+
+    const startHeartbeat = (intervalMs = Math.max(100, Math.floor(opts.staleMs / 3))) => {
+      if (timer) return
+      // Heartbeat prevents long critical sections from being evicted as stale.
+      timer = setInterval(() => {
+        const t = new Date()
+        void utimes(heartbeatPath, t, t).catch(() => undefined)
+      }, intervalMs)
+      timer.unref?.()
+    }
+
+    const release = async () => {
+      if (timer) {
+        clearInterval(timer)
+        timer = undefined
+      }
+
+      const current = await readFile(metaPath, "utf8")
+        .then((raw) => {
+          const parsed = JSON.parse(raw)
+          if (!parsed || typeof parsed !== "object") return {}
+          return {
+            token: "token" in parsed && typeof parsed.token === "string" ? parsed.token : undefined,
+          }
+        })
+        .catch((err) => {
+          const errCode = code(err)
+          if (errCode === "ENOENT" || errCode === "ENOTDIR") {
+            throw new Error("Refusing to release: lock is compromised (metadata missing).")
+          }
+          if (err instanceof SyntaxError) {
+            throw new Error("Refusing to release: lock is compromised (metadata invalid).")
+          }
+          throw err
+        })
+      // Token check prevents deleting a lock that was re-acquired by another process.
+      if (current.token !== token) {
+        throw new Error("Refusing to release: lock token mismatch (not the owner).")
+      }
+
+      await rm(lockDir, { recursive: true, force: true })
+    }
+
+    return {
+      acquired: true,
+      startHeartbeat,
+      release,
+    }
+  }
+
+  async function acquireLockDir(
+    lockDir: string,
+    input: { key: string; onWait?: Wait; signal?: AbortSignal },
+    opts: Opts,
+  ) {
+    const stop = mono() + opts.timeoutMs
+    let attempt = 0
+    let waited = 0
+    let delay = opts.baseDelayMs
+
+    while (true) {
+      input.signal?.throwIfAborted()
+
+      const res = await tryAcquireLockDir(lockDir, opts)
+      if (res.acquired) {
+        return res
+      }
+
+      if (mono() > stop) {
+        throw new Error(`Timed out waiting for lock: ${input.key}`)
+      }
+
+      attempt += 1
+      const ms = jitter(delay)
+      await input.onWait?.({
+        key: input.key,
+        attempt,
+        delay: ms,
+        waited,
+      })
+      await sleep(ms, input.signal)
+      waited += ms
+      delay = Math.min(opts.maxDelayMs, Math.floor(delay * 1.7))
+    }
+  }
+
+  export async function acquire(key: string, input: Options = {}): Promise<Lease> {
+    input.signal?.throwIfAborted()
+    const cfg: Opts = {
+      staleMs: input.staleMs ?? defaultOpts.staleMs,
+      timeoutMs: input.timeoutMs ?? defaultOpts.timeoutMs,
+      baseDelayMs: input.baseDelayMs ?? defaultOpts.baseDelayMs,
+      maxDelayMs: input.maxDelayMs ?? defaultOpts.maxDelayMs,
+    }
+    const dir = input.dir ?? root()
+
+    await mkdir(dir, { recursive: true })
+    const lockfile = path.join(dir, Hash.fast(key) + ".lock")
+    const lock = await acquireLockDir(
+      lockfile,
+      {
+        key,
+        onWait: input.onWait,
+        signal: input.signal,
+      },
+      cfg,
+    )
+    lock.startHeartbeat()
+
+    const release = () => lock.release()
+    return {
+      release,
+      [Symbol.asyncDispose]() {
+        return release()
+      },
+    }
+  }
+
+  export async function withLock<T>(key: string, fn: () => Promise<T>, input: Options = {}) {
+    await using _ = await acquire(key, input)
+    input.signal?.throwIfAborted()
+    return await fn()
+  }
+
+  export const effect = Effect.fn("Flock.effect")(function* (key: string) {
+    return yield* Effect.acquireRelease(
+      Effect.promise((signal) => Flock.acquire(key, { signal })),
+      (foo) => Effect.promise(() => foo.release()),
+    ).pipe(Effect.asVoid)
+  })
+}
--- a/packages/shared/src/util/hash.ts
+++ b/packages/shared/src/util/hash.ts
@@ -0,0 +1,7 @@
+import { createHash } from "crypto"
+
+export namespace Hash {
+  export function fast(input: string | Buffer): string {
+    return createHash("sha1").update(input).digest("hex")
+  }
+}
--- a/packages/shared/test/filesystem/filesystem.test.ts
+++ b/packages/shared/test/filesystem/filesystem.test.ts
@@ -0,0 +1,338 @@
+import { describe, test, expect } from "bun:test"
+import { Effect, Layer, FileSystem } from "effect"
+import { NodeFileSystem } from "@effect/platform-node"
+import { AppFileSystem } from "@opencode-ai/shared/filesystem"
+import { testEffect } from "../lib/effect"
+import path from "path"
+
+const live = AppFileSystem.layer.pipe(Layer.provideMerge(NodeFileSystem.layer))
+const { effect: it } = testEffect(live)
+
+describe("AppFileSystem", () => {
+  describe("isDir", () => {
+    it(
+      "returns true for directories",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        expect(yield* fs.isDir(tmp)).toBe(true)
+      }),
+    )
+
+    it(
+      "returns false for files",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        const file = path.join(tmp, "test.txt")
+        yield* filesys.writeFileString(file, "hello")
+        expect(yield* fs.isDir(file)).toBe(false)
+      }),
+    )
+
+    it(
+      "returns false for non-existent paths",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        expect(yield* fs.isDir("/tmp/nonexistent-" + Math.random())).toBe(false)
+      }),
+    )
+  })
+
+  describe("isFile", () => {
+    it(
+      "returns true for files",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        const file = path.join(tmp, "test.txt")
+        yield* filesys.writeFileString(file, "hello")
+        expect(yield* fs.isFile(file)).toBe(true)
+      }),
+    )
+
+    it(
+      "returns false for directories",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        expect(yield* fs.isFile(tmp)).toBe(false)
+      }),
+    )
+  })
+
+  describe("readJson / writeJson", () => {
+    it(
+      "round-trips JSON data",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        const file = path.join(tmp, "data.json")
+        const data = { name: "test", count: 42, nested: { ok: true } }
+
+        yield* fs.writeJson(file, data)
+        const result = yield* fs.readJson(file)
+
+        expect(result).toEqual(data)
+      }),
+    )
+  })
+
+  describe("ensureDir", () => {
+    it(
+      "creates nested directories",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        const nested = path.join(tmp, "a", "b", "c")
+
+        yield* fs.ensureDir(nested)
+
+        const info = yield* filesys.stat(nested)
+        expect(info.type).toBe("Directory")
+      }),
+    )
+
+    it(
+      "is idempotent",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        const dir = path.join(tmp, "existing")
+        yield* filesys.makeDirectory(dir)
+
+        yield* fs.ensureDir(dir)
+
+        const info = yield* filesys.stat(dir)
+        expect(info.type).toBe("Directory")
+      }),
+    )
+  })
+
+  describe("writeWithDirs", () => {
+    it(
+      "creates parent directories if missing",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        const file = path.join(tmp, "deep", "nested", "file.txt")
+
+        yield* fs.writeWithDirs(file, "hello")
+
+        expect(yield* filesys.readFileString(file)).toBe("hello")
+      }),
+    )
+
+    it(
+      "writes directly when parent exists",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        const file = path.join(tmp, "direct.txt")
+
+        yield* fs.writeWithDirs(file, "world")
+
+        expect(yield* filesys.readFileString(file)).toBe("world")
+      }),
+    )
+
+    it(
+      "writes Uint8Array content",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        const file = path.join(tmp, "binary.bin")
+        const content = new Uint8Array([0x00, 0x01, 0x02, 0x03])
+
+        yield* fs.writeWithDirs(file, content)
+
+        const result = yield* filesys.readFile(file)
+        expect(new Uint8Array(result)).toEqual(content)
+      }),
+    )
+  })
+
+  describe("findUp", () => {
+    it(
+      "finds target in start directory",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        yield* filesys.writeFileString(path.join(tmp, "target.txt"), "found")
+
+        const result = yield* fs.findUp("target.txt", tmp)
+        expect(result).toEqual([path.join(tmp, "target.txt")])
+      }),
+    )
+
+    it(
+      "finds target in parent directories",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        yield* filesys.writeFileString(path.join(tmp, "marker"), "root")
+        const child = path.join(tmp, "a", "b")
+        yield* filesys.makeDirectory(child, { recursive: true })
+
+        const result = yield* fs.findUp("marker", child, tmp)
+        expect(result).toEqual([path.join(tmp, "marker")])
+      }),
+    )
+
+    it(
+      "returns empty array when not found",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        const result = yield* fs.findUp("nonexistent", tmp, tmp)
+        expect(result).toEqual([])
+      }),
+    )
+  })
+
+  describe("up", () => {
+    it(
+      "finds multiple targets walking up",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        yield* filesys.writeFileString(path.join(tmp, "a.txt"), "a")
+        yield* filesys.writeFileString(path.join(tmp, "b.txt"), "b")
+        const child = path.join(tmp, "sub")
+        yield* filesys.makeDirectory(child)
+        yield* filesys.writeFileString(path.join(child, "a.txt"), "a-child")
+
+        const result = yield* fs.up({ targets: ["a.txt", "b.txt"], start: child, stop: tmp })
+
+        expect(result).toContain(path.join(child, "a.txt"))
+        expect(result).toContain(path.join(tmp, "a.txt"))
+        expect(result).toContain(path.join(tmp, "b.txt"))
+      }),
+    )
+  })
+
+  describe("glob", () => {
+    it(
+      "finds files matching pattern",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        yield* filesys.writeFileString(path.join(tmp, "a.ts"), "a")
+        yield* filesys.writeFileString(path.join(tmp, "b.ts"), "b")
+        yield* filesys.writeFileString(path.join(tmp, "c.json"), "c")
+
+        const result = yield* fs.glob("*.ts", { cwd: tmp })
+        expect(result.sort()).toEqual(["a.ts", "b.ts"])
+      }),
+    )
+
+    it(
+      "supports absolute paths",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        yield* filesys.writeFileString(path.join(tmp, "file.txt"), "hello")
+
+        const result = yield* fs.glob("*.txt", { cwd: tmp, absolute: true })
+        expect(result).toEqual([path.join(tmp, "file.txt")])
+      }),
+    )
+  })
+
+  describe("globMatch", () => {
+    it(
+      "matches patterns",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        expect(fs.globMatch("*.ts", "foo.ts")).toBe(true)
+        expect(fs.globMatch("*.ts", "foo.json")).toBe(false)
+        expect(fs.globMatch("src/**", "src/a/b.ts")).toBe(true)
+      }),
+    )
+  })
+
+  describe("globUp", () => {
+    it(
+      "finds files walking up directories",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        yield* filesys.writeFileString(path.join(tmp, "root.md"), "root")
+        const child = path.join(tmp, "a", "b")
+        yield* filesys.makeDirectory(child, { recursive: true })
+        yield* filesys.writeFileString(path.join(child, "leaf.md"), "leaf")
+
+        const result = yield* fs.globUp("*.md", child, tmp)
+        expect(result).toContain(path.join(child, "leaf.md"))
+        expect(result).toContain(path.join(tmp, "root.md"))
+      }),
+    )
+  })
+
+  describe("built-in passthrough", () => {
+    it(
+      "exists works",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        const file = path.join(tmp, "exists.txt")
+        yield* filesys.writeFileString(file, "yes")
+
+        expect(yield* filesys.exists(file)).toBe(true)
+        expect(yield* filesys.exists(file + ".nope")).toBe(false)
+      }),
+    )
+
+    it(
+      "remove works",
+      Effect.gen(function* () {
+        const fs = yield* AppFileSystem.Service
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        const file = path.join(tmp, "delete-me.txt")
+        yield* filesys.writeFileString(file, "bye")
+
+        yield* filesys.remove(file)
+
+        expect(yield* filesys.exists(file)).toBe(false)
+      }),
+    )
+  })
+
+  describe("pure helpers", () => {
+    test("mimeType returns correct types", () => {
+      expect(AppFileSystem.mimeType("file.json")).toBe("application/json")
+      expect(AppFileSystem.mimeType("image.png")).toBe("image/png")
+      expect(AppFileSystem.mimeType("unknown.qzx")).toBe("application/octet-stream")
+    })
+
+    test("contains checks path containment", () => {
+      expect(AppFileSystem.contains("/a/b", "/a/b/c")).toBe(true)
+      expect(AppFileSystem.contains("/a/b", "/a/c")).toBe(false)
+    })
+
+    test("overlaps detects overlapping paths", () => {
+      expect(AppFileSystem.overlaps("/a/b", "/a/b/c")).toBe(true)
+      expect(AppFileSystem.overlaps("/a/b/c", "/a/b")).toBe(true)
+      expect(AppFileSystem.overlaps("/a", "/b")).toBe(false)
+    })
+  })
+})
--- a/packages/shared/test/fixture/flock-worker.ts
+++ b/packages/shared/test/fixture/flock-worker.ts
@@ -0,0 +1,72 @@
+import fs from "fs/promises"
+import { Flock } from "@opencode-ai/shared/util/flock"
+
+type Msg = {
+  key: string
+  dir: string
+  staleMs?: number
+  timeoutMs?: number
+  baseDelayMs?: number
+  maxDelayMs?: number
+  holdMs?: number
+  ready?: string
+  active?: string
+  done?: string
+}
+
+function sleep(ms: number) {
+  return new Promise<void>((resolve) => {
+    setTimeout(resolve, ms)
+  })
+}
+
+function input() {
+  const raw = process.argv[2]
+  if (!raw) {
+    throw new Error("Missing flock worker input")
+  }
+
+  return JSON.parse(raw) as Msg
+}
+
+async function job(input: Msg) {
+  if (input.ready) {
+    await fs.writeFile(input.ready, String(process.pid))
+  }
+
+  if (input.active) {
+    await fs.writeFile(input.active, String(process.pid), { flag: "wx" })
+  }
+
+  try {
+    if (input.holdMs && input.holdMs > 0) {
+      await sleep(input.holdMs)
+    }
+
+    if (input.done) {
+      await fs.appendFile(input.done, "1\n")
+    }
+  } finally {
+    if (input.active) {
+      await fs.rm(input.active, { force: true })
+    }
+  }
+}
+
+async function main() {
+  const msg = input()
+
+  await Flock.withLock(msg.key, () => job(msg), {
+    dir: msg.dir,
+    staleMs: msg.staleMs,
+    timeoutMs: msg.timeoutMs,
+    baseDelayMs: msg.baseDelayMs,
+    maxDelayMs: msg.maxDelayMs,
+  })
+}
+
+await main().catch((err) => {
+  const text = err instanceof Error ? (err.stack ?? err.message) : String(err)
+  process.stderr.write(text)
+  process.exit(1)
+})
--- a/packages/shared/test/lib/effect.ts
+++ b/packages/shared/test/lib/effect.ts
@@ -0,0 +1,53 @@
+import { test, type TestOptions } from "bun:test"
+import { Cause, Effect, Exit, Layer } from "effect"
+import type * as Scope from "effect/Scope"
+import * as TestClock from "effect/testing/TestClock"
+import * as TestConsole from "effect/testing/TestConsole"
+
+type Body<A, E, R> = Effect.Effect<A, E, R> | (() => Effect.Effect<A, E, R>)
+
+const body = <A, E, R>(value: Body<A, E, R>) => Effect.suspend(() => (typeof value === "function" ? value() : value))
+
+const run = <A, E, R, E2>(value: Body<A, E, R | Scope.Scope>, layer: Layer.Layer<R, E2>) =>
+  Effect.gen(function* () {
+    const exit = yield* body(value).pipe(Effect.scoped, Effect.provide(layer), Effect.exit)
+    if (Exit.isFailure(exit)) {
+      for (const err of Cause.prettyErrors(exit.cause)) {
+        yield* Effect.logError(err)
+      }
+    }
+    return yield* exit
+  }).pipe(Effect.runPromise)
+
+const make = <R, E>(testLayer: Layer.Layer<R, E>, liveLayer: Layer.Layer<R, E>) => {
+  const effect = <A, E2>(name: string, value: Body<A, E2, R | Scope.Scope>, opts?: number | TestOptions) =>
+    test(name, () => run(value, testLayer), opts)
+
+  effect.only = <A, E2>(name: string, value: Body<A, E2, R | Scope.Scope>, opts?: number | TestOptions) =>
+    test.only(name, () => run(value, testLayer), opts)
+
+  effect.skip = <A, E2>(name: string, value: Body<A, E2, R | Scope.Scope>, opts?: number | TestOptions) =>
+    test.skip(name, () => run(value, testLayer), opts)
+
+  const live = <A, E2>(name: string, value: Body<A, E2, R | Scope.Scope>, opts?: number | TestOptions) =>
+    test(name, () => run(value, liveLayer), opts)
+
+  live.only = <A, E2>(name: string, value: Body<A, E2, R | Scope.Scope>, opts?: number | TestOptions) =>
+    test.only(name, () => run(value, liveLayer), opts)
+
+  live.skip = <A, E2>(name: string, value: Body<A, E2, R | Scope.Scope>, opts?: number | TestOptions) =>
+    test.skip(name, () => run(value, liveLayer), opts)
+
+  return { effect, live }
+}
+
+// Test environment with TestClock and TestConsole
+const testEnv = Layer.mergeAll(TestConsole.layer, TestClock.layer())
+
+// Live environment - uses real clock, but keeps TestConsole for output capture
+const liveEnv = TestConsole.layer
+
+export const it = make(testEnv, liveEnv)
+
+export const testEffect = <R, E>(layer: Layer.Layer<R, E>) =>
+  make(Layer.provideMerge(layer, testEnv), Layer.provideMerge(layer, liveEnv))
--- a/packages/shared/test/npm.test.ts
+++ b/packages/shared/test/npm.test.ts
@@ -0,0 +1,18 @@
+import { describe, expect, test } from "bun:test"
+import { Npm } from "@opencode-ai/shared/npm"
+
+const win = process.platform === "win32"
+
+describe("Npm.sanitize", () => {
+  test("keeps normal scoped package specs unchanged", () => {
+    expect(Npm.sanitize("@opencode/acme")).toBe("@opencode/acme")
+    expect(Npm.sanitize("@opencode/acme@1.0.0")).toBe("@opencode/acme@1.0.0")
+    expect(Npm.sanitize("prettier")).toBe("prettier")
+  })
+
+  test("handles git https specs", () => {
+    const spec = "acme@git+https://github.com/opencode/acme.git"
+    const expected = win ? "acme@git+https_//github.com/opencode/acme.git" : spec
+    expect(Npm.sanitize(spec)).toBe(expected)
+  })
+})
--- a/packages/shared/test/util/flock.test.ts
+++ b/packages/shared/test/util/flock.test.ts
@@ -0,0 +1,426 @@
+import { describe, expect, test } from "bun:test"
+import fs from "fs/promises"
+import { spawn } from "child_process"
+import path from "path"
+import os from "os"
+import { Flock } from "@opencode-ai/shared/util/flock"
+import { Hash } from "@opencode-ai/shared/util/hash"
+
+type Msg = {
+  key: string
+  dir: string
+  staleMs?: number
+  timeoutMs?: number
+  baseDelayMs?: number
+  maxDelayMs?: number
+  holdMs?: number
+  ready?: string
+  active?: string
+  done?: string
+}
+
+const root = path.join(import.meta.dir, "../..")
+const worker = path.join(import.meta.dir, "../fixture/flock-worker.ts")
+
+async function tmpdir() {
+  const dir = await fs.mkdtemp(path.join(os.tmpdir(), "flock-test-"))
+  return {
+    path: dir,
+    async [Symbol.asyncDispose]() {
+      await fs.rm(dir, { recursive: true, force: true })
+    },
+  }
+}
+
+function lock(dir: string, key: string) {
+  return path.join(dir, Hash.fast(key) + ".lock")
+}
+
+function sleep(ms: number) {
+  return new Promise<void>((resolve) => {
+    setTimeout(resolve, ms)
+  })
+}
+
+async function exists(file: string) {
+  return fs
+    .stat(file)
+    .then(() => true)
+    .catch(() => false)
+}
+
+async function wait(file: string, timeout = 3_000) {
+  const stop = Date.now() + timeout
+  while (Date.now() < stop) {
+    if (await exists(file)) return
+    await sleep(20)
+  }
+
+  throw new Error(`Timed out waiting for file: ${file}`)
+}
+
+function run(msg: Msg) {
+  return new Promise<{ code: number; stdout: Buffer; stderr: Buffer }>((resolve) => {
+    const proc = spawn(process.execPath, [worker, JSON.stringify(msg)], {
+      cwd: root,
+    })
+
+    const stdout: Buffer[] = []
+    const stderr: Buffer[] = []
+
+    proc.stdout?.on("data", (data) => stdout.push(Buffer.from(data)))
+    proc.stderr?.on("data", (data) => stderr.push(Buffer.from(data)))
+
+    proc.on("close", (code) => {
+      resolve({
+        code: code ?? 1,
+        stdout: Buffer.concat(stdout),
+        stderr: Buffer.concat(stderr),
+      })
+    })
+  })
+}
+
+function spawnWorker(msg: Msg) {
+  return spawn(process.execPath, [worker, JSON.stringify(msg)], {
+    cwd: root,
+    stdio: ["ignore", "pipe", "pipe"],
+  })
+}
+
+function stopWorker(proc: ReturnType<typeof spawnWorker>) {
+  if (proc.exitCode !== null || proc.signalCode !== null) return Promise.resolve()
+
+  if (process.platform !== "win32" || !proc.pid) {
+    proc.kill()
+    return Promise.resolve()
+  }
+
+  return new Promise<void>((resolve) => {
+    const killProc = spawn("taskkill", ["/pid", String(proc.pid), "/T", "/F"])
+    killProc.on("close", () => {
+      proc.kill()
+      resolve()
+    })
+  })
+}
+
+async function readJson<T>(p: string): Promise<T> {
+  return JSON.parse(await fs.readFile(p, "utf8"))
+}
+
+describe("util.flock", () => {
+  test("enforces mutual exclusion under process contention", async () => {
+    await using tmp = await tmpdir()
+    const dir = path.join(tmp.path, "locks")
+    const done = path.join(tmp.path, "done.log")
+    const active = path.join(tmp.path, "active")
+    const key = "flock:stress"
+    const n = 16
+
+    const out = await Promise.all(
+      Array.from({ length: n }, () =>
+        run({
+          key,
+          dir,
+          done,
+          active,
+          holdMs: 30,
+          staleMs: 1_000,
+          timeoutMs: 15_000,
+        }),
+      ),
+    )
+
+    expect(out.map((x) => x.code)).toEqual(Array.from({ length: n }, () => 0))
+    expect(out.map((x) => x.stderr.toString()).filter(Boolean)).toEqual([])
+
+    const lines = (await fs.readFile(done, "utf8"))
+      .split("\n")
+      .map((x) => x.trim())
+      .filter(Boolean)
+    expect(lines.length).toBe(n)
+  }, 20_000)
+
+  test("times out while waiting when lock is still healthy", async () => {
+    await using tmp = await tmpdir()
+    const dir = path.join(tmp.path, "locks")
+    const key = "flock:timeout"
+    const ready = path.join(tmp.path, "ready")
+    const proc = spawnWorker({
+      key,
+      dir,
+      ready,
+      holdMs: 20_000,
+      staleMs: 10_000,
+      timeoutMs: 30_000,
+    })
+
+    try {
+      await wait(ready, 5_000)
+      const seen: string[] = []
+      const err = await Flock.withLock(key, async () => {}, {
+        dir,
+        staleMs: 10_000,
+        timeoutMs: 1_000,
+        onWait: (tick) => {
+          seen.push(tick.key)
+        },
+      }).catch((err) => err)
+
+      expect(err).toBeInstanceOf(Error)
+      if (!(err instanceof Error)) throw err
+      expect(err.message).toContain("Timed out waiting for lock")
+      expect(seen.length).toBeGreaterThan(0)
+      expect(seen.every((x) => x === key)).toBe(true)
+    } finally {
+      await stopWorker(proc).catch(() => undefined)
+      await new Promise((resolve) => proc.on("close", resolve))
+    }
+  }, 15_000)
+
+  test("recovers after a crashed lock owner", async () => {
+    await using tmp = await tmpdir()
+    const dir = path.join(tmp.path, "locks")
+    const key = "flock:crash"
+    const ready = path.join(tmp.path, "ready")
+    const proc = spawnWorker({
+      key,
+      dir,
+      ready,
+      holdMs: 20_000,
+      staleMs: 500,
+      timeoutMs: 30_000,
+    })
+
+    await wait(ready, 5_000)
+    await stopWorker(proc)
+    await new Promise((resolve) => proc.on("close", resolve))
+
+    let hit = false
+    await Flock.withLock(
+      key,
+      async () => {
+        hit = true
+      },
+      {
+        dir,
+        staleMs: 500,
+        timeoutMs: 8_000,
+      },
+    )
+
+    expect(hit).toBe(true)
+  }, 20_000)
+
+  test("breaks stale lock dirs when heartbeat is missing", async () => {
+    await using tmp = await tmpdir()
+    const dir = path.join(tmp.path, "locks")
+    const key = "flock:missing-heartbeat"
+    const lockDir = lock(dir, key)
+
+    await fs.mkdir(lockDir, { recursive: true })
+    const old = new Date(Date.now() - 2_000)
+    await fs.utimes(lockDir, old, old)
+
+    let hit = false
+    await Flock.withLock(
+      key,
+      async () => {
+        hit = true
+      },
+      {
+        dir,
+        staleMs: 200,
+        timeoutMs: 3_000,
+      },
+    )
+
+    expect(hit).toBe(true)
+  })
+
+  test("recovers when a stale breaker claim was left behind", async () => {
+    await using tmp = await tmpdir()
+    const dir = path.join(tmp.path, "locks")
+    const key = "flock:stale-breaker"
+    const lockDir = lock(dir, key)
+    const breaker = lockDir + ".breaker"
+
+    await fs.mkdir(lockDir, { recursive: true })
+    await fs.mkdir(breaker)
+
+    const old = new Date(Date.now() - 2_000)
+    await fs.utimes(lockDir, old, old)
+    await fs.utimes(breaker, old, old)
+
+    let hit = false
+    await Flock.withLock(
+      key,
+      async () => {
+        hit = true
+      },
+      {
+        dir,
+        staleMs: 200,
+        timeoutMs: 3_000,
+      },
+    )
+
+    expect(hit).toBe(true)
+    expect(await exists(breaker)).toBe(false)
+  })
+
+  test("fails clearly if lock dir is removed while held", async () => {
+    await using tmp = await tmpdir()
+    const dir = path.join(tmp.path, "locks")
+    const key = "flock:compromised"
+    const lockDir = lock(dir, key)
+
+    const err = await Flock.withLock(
+      key,
+      async () => {
+        await fs.rm(lockDir, {
+          recursive: true,
+          force: true,
+        })
+      },
+      {
+        dir,
+        staleMs: 1_000,
+        timeoutMs: 3_000,
+      },
+    ).catch((err) => err)
+
+    expect(err).toBeInstanceOf(Error)
+    if (!(err instanceof Error)) throw err
+    expect(err.message).toContain("compromised")
+
+    let hit = false
+    await Flock.withLock(
+      key,
+      async () => {
+        hit = true
+      },
+      {
+        dir,
+        staleMs: 200,
+        timeoutMs: 3_000,
+      },
+    )
+    expect(hit).toBe(true)
+  })
+
+  test("writes owner metadata while lock is held", async () => {
+    await using tmp = await tmpdir()
+    const dir = path.join(tmp.path, "locks")
+    const key = "flock:meta"
+    const file = path.join(lock(dir, key), "meta.json")
+
+    await Flock.withLock(
+      key,
+      async () => {
+        const json = await readJson<{
+          token?: unknown
+          pid?: unknown
+          hostname?: unknown
+          createdAt?: unknown
+        }>(file)
+
+        expect(typeof json.token).toBe("string")
+        expect(typeof json.pid).toBe("number")
+        expect(typeof json.hostname).toBe("string")
+        expect(typeof json.createdAt).toBe("string")
+      },
+      {
+        dir,
+        staleMs: 1_000,
+        timeoutMs: 3_000,
+      },
+    )
+  })
+
+  test("supports acquire with await using", async () => {
+    await using tmp = await tmpdir()
+    const dir = path.join(tmp.path, "locks")
+    const key = "flock:acquire"
+    const lockDir = lock(dir, key)
+
+    {
+      await using _ = await Flock.acquire(key, {
+        dir,
+        staleMs: 1_000,
+        timeoutMs: 3_000,
+      })
+      expect(await exists(lockDir)).toBe(true)
+    }
+
+    expect(await exists(lockDir)).toBe(false)
+  })
+
+  test("refuses token mismatch release and recovers from stale", async () => {
+    await using tmp = await tmpdir()
+    const dir = path.join(tmp.path, "locks")
+    const key = "flock:token"
+    const lockDir = lock(dir, key)
+    const meta = path.join(lockDir, "meta.json")
+
+    const err = await Flock.withLock(
+      key,
+      async () => {
+        const json = await readJson<{ token?: string }>(meta)
+        json.token = "tampered"
+        await fs.writeFile(meta, JSON.stringify(json, null, 2))
+      },
+      {
+        dir,
+        staleMs: 500,
+        timeoutMs: 3_000,
+      },
+    ).catch((err) => err)
+
+    expect(err).toBeInstanceOf(Error)
+    if (!(err instanceof Error)) throw err
+    expect(err.message).toContain("token mismatch")
+    expect(await exists(lockDir)).toBe(true)
+
+    let hit = false
+    await Flock.withLock(
+      key,
+      async () => {
+        hit = true
+      },
+      {
+        dir,
+        staleMs: 500,
+        timeoutMs: 6_000,
+      },
+    )
+    expect(hit).toBe(true)
+  })
+
+  test("fails clearly on unwritable lock roots", async () => {
+    if (process.platform === "win32") return
+
+    await using tmp = await tmpdir()
+    const dir = path.join(tmp.path, "locks")
+    const key = "flock:perm"
+
+    await fs.mkdir(dir, { recursive: true })
+    await fs.chmod(dir, 0o500)
+
+    try {
+      const err = await Flock.withLock(key, async () => {}, {
+        dir,
+        staleMs: 100,
+        timeoutMs: 500,
+      }).catch((err) => err)
+
+      expect(err).toBeInstanceOf(Error)
+      if (!(err instanceof Error)) throw err
+      const text = err.message
+      expect(text.includes("EACCES") || text.includes("EPERM")).toBe(true)
+    } finally {
+      await fs.chmod(dir, 0o700)
+    }
+  })
+})