refactor(file-time): effectify FileTimeService with Semaphore locks

Convert FileTime from Instance.state to Effect ServiceMap.Service.
Replace hand-rolled Promise lock chain with SynchronizedRef<Map> +
Semaphore.withPermits for per-file mutual exclusion. Legacy facade
preserved — callers unchanged.

packages/opencode/AGENTS.md

@@ -34,6 +34,7 @@ Instructions to follow when writing Effect.
 - Use `Effect.gen(function* () { ... })` for composition.
 - Use `Effect.fn("ServiceName.method")` for named/traced effects and `Effect.fnUntraced` for internal helpers.
 - `Effect.fn` / `Effect.fnUntraced` accept pipeable operators as extra arguments, so avoid unnecessary `flow` or outer `.pipe()` wrappers.
+- **`Effect.callback`** (not `Effect.async`) for callback-based APIs. The classic `Effect.async` was renamed to `Effect.callback` in effect-smol/v4.
 
 ## Time
 
@@ -42,3 +43,37 @@ Instructions to follow when writing Effect.
 ## Errors
 
 - In `Effect.gen/fn`, prefer `yield* new MyError(...)` over `yield* Effect.fail(new MyError(...))` for direct early-failure branches.
+
+## Instance-scoped Effect services
+
+Services that need per-directory lifecycle (created/destroyed per instance) go through the `Instances` LayerMap:
+
+1. Define a `ServiceMap.Service` with a `static readonly layer` (see `FileWatcherService`, `QuestionService`, `PermissionService`, `ProviderAuthService`).
+2. Add it to `InstanceServices` union and `Layer.mergeAll(...)` in `src/effect/instances.ts`.
+3. Use `InstanceContext` inside the layer to read `directory` and `project` instead of `Instance.*` globals.
+4. Call from legacy code via `runPromiseInstance(MyService.use((s) => s.method()))`.
+
+### Instance.bind — ALS context for native callbacks
+
+`Instance.bind(fn)` captures the current Instance AsyncLocalStorage context and returns a wrapper that restores it synchronously when called.
+
+**Use it** when passing callbacks to native C/C++ addons (`@parcel/watcher`, `node-pty`, native `fs.watch`, etc.) that need to call `Bus.publish`, `Instance.state()`, or anything that reads `Instance.directory`.
+
+**Don't need it** for `setTimeout`, `Promise.then`, `EventEmitter.on`, or Effect fibers — Node.js ALS propagates through those automatically.
+
+```typescript
+// Native addon callback — needs Instance.bind
+const cb = Instance.bind((err, evts) => {
+  Bus.publish(MyEvent, { ... })
+})
+nativeAddon.subscribe(dir, cb)
+```
+
+## Flag → Effect.Config migration
+
+Flags in `src/flag/flag.ts` are being migrated from static `truthy(...)` reads to `Config.boolean(...).pipe(Config.withDefault(false))` as their consumers get effectified.
+
+- Effectful flags return `Config<boolean>` and are read with `yield*` inside `Effect.gen`.
+- The default `ConfigProvider` reads from `process.env`, so env vars keep working.
+- Tests can override via `ConfigProvider.layer(ConfigProvider.fromUnknown({ ... }))`.
+- Keep all flags in `flag.ts` as the single registry — just change the implementation from `truthy()` to `Config.boolean()` when the consumer moves to Effect.

packages/opencode/src/effect/instance-context.ts

@@ -0,0 +1,13 @@
+import { ServiceMap } from "effect"
+import type { Project } from "@/project/project"
+
+export declare namespace InstanceContext {
+  export interface Shape {
+    readonly directory: string
+    readonly project: Project.Info
+  }
+}
+
+export class InstanceContext extends ServiceMap.Service<InstanceContext, InstanceContext.Shape>()(
+  "opencode/InstanceContext",
+) {}

packages/opencode/src/effect/instances.ts

@@ -1,23 +1,23 @@
 import { Effect, Layer, LayerMap, ServiceMap } from "effect"
 import { registerDisposer } from "./instance-registry"
+import { InstanceContext } from "./instance-context"
 import { ProviderAuthService } from "@/provider/auth-service"
 import { QuestionService } from "@/question/service"
 import { PermissionService } from "@/permission/service"
+import { FileWatcherService } from "@/file/watcher"
+import { VcsService } from "@/project/vcs"
+import { FileTimeService } from "@/file/time"
 import { Instance } from "@/project/instance"
-import type { Project } from "@/project/project"
 
-export declare namespace InstanceContext {
-  export interface Shape {
-    readonly directory: string
-    readonly project: Project.Info
-  }
-}
+export { InstanceContext } from "./instance-context"
 
-export class InstanceContext extends ServiceMap.Service<InstanceContext, InstanceContext.Shape>()(
-  "opencode/InstanceContext",
-) {}
-
-export type InstanceServices = QuestionService | PermissionService | ProviderAuthService
+export type InstanceServices =
+  | QuestionService
+  | PermissionService
+  | ProviderAuthService
+  | FileWatcherService
+  | VcsService
+  | FileTimeService
 
 function lookup(directory: string) {
   const project = Instance.project
@@ -26,7 +26,10 @@ function lookup(directory: string) {
     Layer.fresh(QuestionService.layer),
     Layer.fresh(PermissionService.layer),
     Layer.fresh(ProviderAuthService.layer),
-  ).pipe(Layer.provide(ctx))
+    Layer.fresh(FileWatcherService.layer),
+    Layer.fresh(VcsService.layer),
+    Layer.fresh(FileTimeService.layer),
+  ).pipe(Layer.provide(ctx), Layer.orDie)
 }
 
 export class Instances extends ServiceMap.Service<Instances, LayerMap.LayerMap<string, InstanceServices>>()(

packages/opencode/src/file/time.ts

@@ -1,71 +1,88 @@
-import { Instance } from "../project/instance"
 import { Log } from "../util/log"
-import { Flag } from "../flag/flag"
+import { Flag } from "@/flag/flag"
 import { Filesystem } from "../util/filesystem"
+import { Effect, Layer, ServiceMap, Semaphore } from "effect"
+import { runPromiseInstance } from "@/effect/runtime"
 
-export namespace FileTime {
-  const log = Log.create({ service: "file.time" })
-  // Per-session read times plus per-file write locks.
-  // All tools that overwrite existing files should run their
-  // assert/read/write/update sequence inside withLock(filepath, ...)
-  // so concurrent writes to the same file are serialized.
-  export const state = Instance.state(() => {
-    const read: {
-      [sessionID: string]: {
-        [path: string]: Date | undefined
+const log = Log.create({ service: "file.time" })
+
+export namespace FileTimeService {
+  export interface Service {
+    readonly read: (sessionID: string, file: string) => Effect.Effect<void>
+    readonly get: (sessionID: string, file: string) => Effect.Effect<Date | undefined>
+    readonly assert: (sessionID: string, filepath: string) => Effect.Effect<void>
+    readonly withLock: <T>(filepath: string, fn: () => Promise<T>) => Effect.Effect<T>
+  }
+}
+
+export class FileTimeService extends ServiceMap.Service<FileTimeService, FileTimeService.Service>()(
+  "@opencode/FileTime",
+) {
+  static readonly layer = Layer.effect(
+    FileTimeService,
+    Effect.gen(function* () {
+      const disableCheck = yield* Flag.OPENCODE_DISABLE_FILETIME_CHECK
+      const reads: { [sessionID: string]: { [path: string]: Date | undefined } } = {}
+      const locks = new Map<string, Semaphore.Semaphore>()
+
+      function getLock(filepath: string) {
+        let lock = locks.get(filepath)
+        if (!lock) {
+          lock = Semaphore.makeUnsafe(1)
+          locks.set(filepath, lock)
+        }
+        return lock
       }
-    } = {}
-    const locks = new Map<string, Promise<void>>()
-    return {
-      read,
-      locks,
-    }
-  })
 
+      return FileTimeService.of({
+        read: Effect.fn("FileTimeService.read")(function* (sessionID: string, file: string) {
+          log.info("read", { sessionID, file })
+          reads[sessionID] = reads[sessionID] || {}
+          reads[sessionID][file] = new Date()
+        }),
+
+        get: Effect.fn("FileTimeService.get")(function* (sessionID: string, file: string) {
+          return reads[sessionID]?.[file]
+        }),
+
+        assert: Effect.fn("FileTimeService.assert")(function* (sessionID: string, filepath: string) {
+          if (disableCheck) return
+
+          const time = reads[sessionID]?.[filepath]
+          if (!time) throw new Error(`You must read file ${filepath} before overwriting it. Use the Read tool first`)
+          const mtime = Filesystem.stat(filepath)?.mtime
+          if (mtime && mtime.getTime() > time.getTime() + 50) {
+            throw new Error(
+              `File ${filepath} has been modified since it was last read.\nLast modification: ${mtime.toISOString()}\nLast read: ${time.toISOString()}\n\nPlease read the file again before modifying it.`,
+            )
+          }
+        }),
+
+        withLock: Effect.fn("FileTimeService.withLock")(function* <T>(filepath: string, fn: () => Promise<T>) {
+          const lock = getLock(filepath)
+          return yield* Effect.promise(fn).pipe(lock.withPermits(1))
+        }),
+      })
+    }),
+  )
+}
+
+// Legacy facade — callers don't need to change
+export namespace FileTime {
   export function read(sessionID: string, file: string) {
-    log.info("read", { sessionID, file })
-    const { read } = state()
-    read[sessionID] = read[sessionID] || {}
-    read[sessionID][file] = new Date()
+    // Fire-and-forget — callers never await this
+    runPromiseInstance(FileTimeService.use((s) => s.read(sessionID, file)))
   }
 
   export function get(sessionID: string, file: string) {
-    return state().read[sessionID]?.[file]
-  }
-
-  export async function withLock<T>(filepath: string, fn: () => Promise<T>): Promise<T> {
-    const current = state()
-    const currentLock = current.locks.get(filepath) ?? Promise.resolve()
-    let release: () => void = () => {}
-    const nextLock = new Promise<void>((resolve) => {
-      release = resolve
-    })
-    const chained = currentLock.then(() => nextLock)
-    current.locks.set(filepath, chained)
-    await currentLock
-    try {
-      return await fn()
-    } finally {
-      release()
-      if (current.locks.get(filepath) === chained) {
-        current.locks.delete(filepath)
-      }
-    }
+    return runPromiseInstance(FileTimeService.use((s) => s.get(sessionID, file)))
   }
 
   export async function assert(sessionID: string, filepath: string) {
-    if (Flag.OPENCODE_DISABLE_FILETIME_CHECK === true) {
-      return
-    }
+    return runPromiseInstance(FileTimeService.use((s) => s.assert(sessionID, filepath)))
+  }
 
-    const time = get(sessionID, filepath)
-    if (!time) throw new Error(`You must read file ${filepath} before overwriting it. Use the Read tool first`)
-    const mtime = Filesystem.stat(filepath)?.mtime
-    // Allow a 50ms tolerance for Windows NTFS timestamp fuzziness / async flushing
-    if (mtime && mtime.getTime() > time.getTime() + 50) {
-      throw new Error(
-        `File ${filepath} has been modified since it was last read.\nLast modification: ${mtime.toISOString()}\nLast read: ${time.toISOString()}\n\nPlease read the file again before modifying it.`,
-      )
-    }
+  export async function withLock<T>(filepath: string, fn: () => Promise<T>): Promise<T> {
+    return runPromiseInstance(FileTimeService.use((s) => s.withLock(filepath, fn)))
   }
 }

packages/opencode/src/file/watcher.ts

@@ -1,7 +1,8 @@
 import { BusEvent } from "@/bus/bus-event"
 import { Bus } from "@/bus"
+import { InstanceContext } from "@/effect/instance-context"
+import { Instance } from "@/project/instance"
 import z from "zod"
-import { Instance } from "../project/instance"
 import { Log } from "../util/log"
 import { FileIgnore } from "./ignore"
 import { Config } from "../config/config"
@@ -9,118 +10,139 @@ import path from "path"
 // @ts-ignore
 import { createWrapper } from "@parcel/watcher/wrapper"
 import { lazy } from "@/util/lazy"
-import { withTimeout } from "@/util/timeout"
 import type ParcelWatcher from "@parcel/watcher"
-import { Flag } from "@/flag/flag"
 import { readdir } from "fs/promises"
 import { git } from "@/util/git"
 import { Protected } from "./protected"
+import { Flag } from "@/flag/flag"
+import { Cause, Effect, Layer, ServiceMap } from "effect"
 
 const SUBSCRIBE_TIMEOUT_MS = 10_000
 
 declare const OPENCODE_LIBC: string | undefined
 
-export namespace FileWatcher {
-  const log = Log.create({ service: "file.watcher" })
+const log = Log.create({ service: "file.watcher" })
 
-  export const Event = {
-    Updated: BusEvent.define(
-      "file.watcher.updated",
-      z.object({
-        file: z.string(),
-        event: z.union([z.literal("add"), z.literal("change"), z.literal("unlink")]),
-      }),
-    ),
+const event = {
+  Updated: BusEvent.define(
+    "file.watcher.updated",
+    z.object({
+      file: z.string(),
+      event: z.union([z.literal("add"), z.literal("change"), z.literal("unlink")]),
+    }),
+  ),
+}
+
+const watcher = lazy((): typeof import("@parcel/watcher") | undefined => {
+  try {
+    const binding = require(
+      `@parcel/watcher-${process.platform}-${process.arch}${process.platform === "linux" ? `-${OPENCODE_LIBC || "glibc"}` : ""}`,
+    )
+    return createWrapper(binding) as typeof import("@parcel/watcher")
+  } catch (error) {
+    log.error("failed to load watcher binding", { error })
+    return
   }
+})
 
-  const watcher = lazy((): typeof import("@parcel/watcher") | undefined => {
-    try {
-      const binding = require(
-        `@parcel/watcher-${process.platform}-${process.arch}${process.platform === "linux" ? `-${OPENCODE_LIBC || "glibc"}` : ""}`,
-      )
-      return createWrapper(binding) as typeof import("@parcel/watcher")
-    } catch (error) {
-      log.error("failed to load watcher binding", { error })
-      return
-    }
-  })
+function getBackend() {
+  if (process.platform === "win32") return "windows"
+  if (process.platform === "darwin") return "fs-events"
+  if (process.platform === "linux") return "inotify"
+}
 
-  const state = Instance.state(
-    async () => {
-      log.info("init")
-      const cfg = await Config.get()
-      const backend = (() => {
-        if (process.platform === "win32") return "windows"
-        if (process.platform === "darwin") return "fs-events"
-        if (process.platform === "linux") return "inotify"
-      })()
-      if (!backend) {
-        log.error("watcher backend not supported", { platform: process.platform })
-        return {}
-      }
-      log.info("watcher backend", { platform: process.platform, backend })
+export namespace FileWatcher {
+  export const Event = event
+  /** Whether the native @parcel/watcher binding is available on this platform. */
+  export const hasNativeBinding = () => !!watcher()
+}
 
-      const w = watcher()
-      if (!w) return {}
+const init = Effect.fn("FileWatcherService.init")(function* () {})
 
-      const subscribe: ParcelWatcher.SubscribeCallback = (err, evts) => {
-        if (err) return
-        for (const evt of evts) {
-          if (evt.type === "create") Bus.publish(Event.Updated, { file: evt.path, event: "add" })
-          if (evt.type === "update") Bus.publish(Event.Updated, { file: evt.path, event: "change" })
-          if (evt.type === "delete") Bus.publish(Event.Updated, { file: evt.path, event: "unlink" })
-        }
-      }
-
-      const subs: ParcelWatcher.AsyncSubscription[] = []
-      const cfgIgnores = cfg.watcher?.ignore ?? []
-
-      if (Flag.OPENCODE_EXPERIMENTAL_FILEWATCHER) {
-        const pending = w.subscribe(Instance.directory, subscribe, {
-          ignore: [...FileIgnore.PATTERNS, ...cfgIgnores, ...Protected.paths()],
-          backend,
-        })
-        const sub = await withTimeout(pending, SUBSCRIBE_TIMEOUT_MS).catch((err) => {
-          log.error("failed to subscribe to Instance.directory", { error: err })
-          pending.then((s) => s.unsubscribe()).catch(() => {})
-          return undefined
-        })
-        if (sub) subs.push(sub)
-      }
-
-      if (Instance.project.vcs === "git") {
-        const result = await git(["rev-parse", "--git-dir"], {
-          cwd: Instance.worktree,
-        })
-        const vcsDir = result.exitCode === 0 ? path.resolve(Instance.worktree, result.text().trim()) : undefined
-        if (vcsDir && !cfgIgnores.includes(".git") && !cfgIgnores.includes(vcsDir)) {
-          const gitDirContents = await readdir(vcsDir).catch(() => [])
-          const ignoreList = gitDirContents.filter((entry) => entry !== "HEAD")
-          const pending = w.subscribe(vcsDir, subscribe, {
-            ignore: ignoreList,
-            backend,
-          })
-          const sub = await withTimeout(pending, SUBSCRIBE_TIMEOUT_MS).catch((err) => {
-            log.error("failed to subscribe to vcsDir", { error: err })
-            pending.then((s) => s.unsubscribe()).catch(() => {})
-            return undefined
-          })
-          if (sub) subs.push(sub)
-        }
-      }
-
-      return { subs }
-    },
-    async (state) => {
-      if (!state.subs) return
-      await Promise.all(state.subs.map((sub) => sub?.unsubscribe()))
-    },
-  )
-
-  export function init() {
-    if (Flag.OPENCODE_EXPERIMENTAL_DISABLE_FILEWATCHER) {
-      return
-    }
-    state()
+export namespace FileWatcherService {
+  export interface Service {
+    readonly init: () => Effect.Effect<void>
   }
 }
+
+export class FileWatcherService extends ServiceMap.Service<FileWatcherService, FileWatcherService.Service>()(
+  "@opencode/FileWatcher",
+) {
+  static readonly layer = Layer.effect(
+    FileWatcherService,
+    Effect.gen(function* () {
+      const instance = yield* InstanceContext
+      if (yield* Flag.OPENCODE_EXPERIMENTAL_DISABLE_FILEWATCHER) return FileWatcherService.of({ init })
+
+      log.info("init", { directory: instance.directory })
+
+      const backend = getBackend()
+      if (!backend) {
+        log.error("watcher backend not supported", { directory: instance.directory, platform: process.platform })
+        return FileWatcherService.of({ init })
+      }
+
+      const w = watcher()
+      if (!w) return FileWatcherService.of({ init })
+
+      log.info("watcher backend", { directory: instance.directory, platform: process.platform, backend })
+
+      const subs: ParcelWatcher.AsyncSubscription[] = []
+      yield* Effect.addFinalizer(() => Effect.promise(() => Promise.allSettled(subs.map((sub) => sub.unsubscribe()))))
+
+      const cb: ParcelWatcher.SubscribeCallback = Instance.bind((err, evts) => {
+        if (err) return
+        for (const evt of evts) {
+          if (evt.type === "create") Bus.publish(event.Updated, { file: evt.path, event: "add" })
+          if (evt.type === "update") Bus.publish(event.Updated, { file: evt.path, event: "change" })
+          if (evt.type === "delete") Bus.publish(event.Updated, { file: evt.path, event: "unlink" })
+        }
+      })
+
+      const subscribe = (dir: string, ignore: string[]) => {
+        const pending = w.subscribe(dir, cb, { ignore, backend })
+        return Effect.gen(function* () {
+          const sub = yield* Effect.promise(() => pending)
+          subs.push(sub)
+        }).pipe(
+          Effect.timeout(SUBSCRIBE_TIMEOUT_MS),
+          Effect.catchCause((cause) => {
+            log.error("failed to subscribe", { dir, cause: Cause.pretty(cause) })
+            // Clean up a subscription that resolves after timeout
+            pending.then((s) => s.unsubscribe()).catch(() => {})
+            return Effect.void
+          }),
+        )
+      }
+
+      const cfg = yield* Effect.promise(() => Config.get())
+      const cfgIgnores = cfg.watcher?.ignore ?? []
+
+      if (yield* Flag.OPENCODE_EXPERIMENTAL_FILEWATCHER) {
+        yield* subscribe(instance.directory, [...FileIgnore.PATTERNS, ...cfgIgnores, ...Protected.paths()])
+      }
+
+      if (instance.project.vcs === "git") {
+        const result = yield* Effect.promise(() =>
+          git(["rev-parse", "--git-dir"], {
+            cwd: instance.project.worktree,
+          }),
+        )
+        const vcsDir = result.exitCode === 0 ? path.resolve(instance.project.worktree, result.text().trim()) : undefined
+        if (vcsDir && !cfgIgnores.includes(".git") && !cfgIgnores.includes(vcsDir)) {
+          const ignore = (yield* Effect.promise(() => readdir(vcsDir).catch(() => []))).filter(
+            (entry) => entry !== "HEAD",
+          )
+          yield* subscribe(vcsDir, ignore)
+        }
+      }
+
+      return FileWatcherService.of({ init })
+    }).pipe(
+      Effect.catchCause((cause) => {
+        log.error("failed to init watcher service", { cause: Cause.pretty(cause) })
+        return Effect.succeed(FileWatcherService.of({ init }))
+      }),
+    ),
+  )
+}

packages/opencode/src/flag/flag.ts

@@ -1,3 +1,5 @@
+import { Config } from "effect"
+
 function truthy(key: string) {
   const value = process.env[key]?.toLowerCase()
   return value === "true" || value === "1"
@@ -40,8 +42,12 @@ export namespace Flag {
 
   // Experimental
   export const OPENCODE_EXPERIMENTAL = truthy("OPENCODE_EXPERIMENTAL")
-  export const OPENCODE_EXPERIMENTAL_FILEWATCHER = truthy("OPENCODE_EXPERIMENTAL_FILEWATCHER")
-  export const OPENCODE_EXPERIMENTAL_DISABLE_FILEWATCHER = truthy("OPENCODE_EXPERIMENTAL_DISABLE_FILEWATCHER")
+  export const OPENCODE_EXPERIMENTAL_FILEWATCHER = Config.boolean("OPENCODE_EXPERIMENTAL_FILEWATCHER").pipe(
+    Config.withDefault(false),
+  )
+  export const OPENCODE_EXPERIMENTAL_DISABLE_FILEWATCHER = Config.boolean(
+    "OPENCODE_EXPERIMENTAL_DISABLE_FILEWATCHER",
+  ).pipe(Config.withDefault(false))
   export const OPENCODE_EXPERIMENTAL_ICON_DISCOVERY =
     OPENCODE_EXPERIMENTAL || truthy("OPENCODE_EXPERIMENTAL_ICON_DISCOVERY")
 
@@ -55,7 +61,9 @@ export namespace Flag {
   export const OPENCODE_EXPERIMENTAL_OXFMT = OPENCODE_EXPERIMENTAL || truthy("OPENCODE_EXPERIMENTAL_OXFMT")
   export const OPENCODE_EXPERIMENTAL_LSP_TY = truthy("OPENCODE_EXPERIMENTAL_LSP_TY")
   export const OPENCODE_EXPERIMENTAL_LSP_TOOL = OPENCODE_EXPERIMENTAL || truthy("OPENCODE_EXPERIMENTAL_LSP_TOOL")
-  export const OPENCODE_DISABLE_FILETIME_CHECK = truthy("OPENCODE_DISABLE_FILETIME_CHECK")
+  export const OPENCODE_DISABLE_FILETIME_CHECK = Config.boolean("OPENCODE_DISABLE_FILETIME_CHECK").pipe(
+    Config.withDefault(false),
+  )
   export const OPENCODE_EXPERIMENTAL_PLAN_MODE = OPENCODE_EXPERIMENTAL || truthy("OPENCODE_EXPERIMENTAL_PLAN_MODE")
   export const OPENCODE_EXPERIMENTAL_WORKSPACES = OPENCODE_EXPERIMENTAL || truthy("OPENCODE_EXPERIMENTAL_WORKSPACES")
   export const OPENCODE_EXPERIMENTAL_MARKDOWN = !falsy("OPENCODE_EXPERIMENTAL_MARKDOWN")

packages/opencode/src/permission/service.ts

@@ -1,6 +1,6 @@
 import { Bus } from "@/bus"
 import { BusEvent } from "@/bus/bus-event"
-import { InstanceContext } from "@/effect/instances"
+import { InstanceContext } from "@/effect/instance-context"
 import { ProjectID } from "@/project/schema"
 import { MessageID, SessionID } from "@/session/schema"
 import { PermissionTable } from "@/session/session.sql"

packages/opencode/src/project/bootstrap.ts

@@ -1,17 +1,18 @@
 import { Plugin } from "../plugin"
 import { Format } from "../format"
 import { LSP } from "../lsp"
-import { FileWatcher } from "../file/watcher"
+import { FileWatcherService } from "../file/watcher"
 import { File } from "../file"
 import { Project } from "./project"
 import { Bus } from "../bus"
 import { Command } from "../command"
 import { Instance } from "./instance"
-import { Vcs } from "./vcs"
+import { VcsService } from "./vcs"
 import { Log } from "@/util/log"
 import { ShareNext } from "@/share/share-next"
 import { Snapshot } from "../snapshot"
 import { Truncate } from "../tool/truncation"
+import { runPromiseInstance } from "@/effect/runtime"
 
 export async function InstanceBootstrap() {
   Log.Default.info("bootstrapping", { directory: Instance.directory })
@@ -19,9 +20,9 @@ export async function InstanceBootstrap() {
   ShareNext.init()
   Format.init()
   await LSP.init()
-  FileWatcher.init()
+  await runPromiseInstance(FileWatcherService.use((service) => service.init()))
   File.init()
-  Vcs.init()
+  await runPromiseInstance(VcsService.use((s) => s.init()))
   Snapshot.init()
   Truncate.init()
 

packages/opencode/src/project/instance.ts

@@ -101,6 +101,15 @@ export const Instance = {
     if (Instance.worktree === "/") return false
     return Filesystem.contains(Instance.worktree, filepath)
   },
+  /**
+   * Captures the current instance ALS context and returns a wrapper that
+   * restores it when called. Use this for callbacks that fire outside the
+   * instance async context (native addons, event emitters, timers, etc.).
+   */
+  bind<F extends (...args: any[]) => any>(fn: F): F {
+    const ctx = context.use()
+    return ((...args: any[]) => context.provide(ctx, () => fn(...args))) as F
+  },
   state<S>(init: () => S, dispose?: (state: Awaited<S>) => Promise<void>): () => S {
     return State.create(() => Instance.directory, init, dispose)
   },

packages/opencode/src/project/vcs.ts

@@ -1,11 +1,12 @@
 import { BusEvent } from "@/bus/bus-event"
 import { Bus } from "@/bus"
-import path from "path"
 import z from "zod"
 import { Log } from "@/util/log"
 import { Instance } from "./instance"
+import { InstanceContext } from "@/effect/instance-context"
 import { FileWatcher } from "@/file/watcher"
 import { git } from "@/util/git"
+import { Effect, Layer, ServiceMap } from "effect"
 
 const log = Log.create({ service: "vcs" })
 
@@ -27,50 +28,57 @@ export namespace Vcs {
       ref: "VcsInfo",
     })
   export type Info = z.infer<typeof Info>
+}
 
-  async function currentBranch() {
-    const result = await git(["rev-parse", "--abbrev-ref", "HEAD"], {
-      cwd: Instance.worktree,
-    })
-    if (result.exitCode !== 0) return
-    const text = result.text().trim()
-    if (!text) return
-    return text
-  }
-
-  const state = Instance.state(
-    async () => {
-      if (Instance.project.vcs !== "git") {
-        return { branch: async () => undefined, unsubscribe: undefined }
-      }
-      let current = await currentBranch()
-      log.info("initialized", { branch: current })
-
-      const unsubscribe = Bus.subscribe(FileWatcher.Event.Updated, async (evt) => {
-        if (evt.properties.file.endsWith("HEAD")) return
-        const next = await currentBranch()
-        if (next !== current) {
-          log.info("branch changed", { from: current, to: next })
-          current = next
-          Bus.publish(Event.BranchUpdated, { branch: next })
-        }
-      })
-
-      return {
-        branch: async () => current,
-        unsubscribe,
-      }
-    },
-    async (state) => {
-      state.unsubscribe?.()
-    },
-  )
-
-  export async function init() {
-    return state()
-  }
-
-  export async function branch() {
-    return await state().then((s) => s.branch())
+export namespace VcsService {
+  export interface Service {
+    readonly init: () => Effect.Effect<void>
+    readonly branch: () => Effect.Effect<string | undefined>
   }
 }
+
+export class VcsService extends ServiceMap.Service<VcsService, VcsService.Service>()("@opencode/Vcs") {
+  static readonly layer = Layer.effect(
+    VcsService,
+    Effect.gen(function* () {
+      const instance = yield* InstanceContext
+      let current: string | undefined
+
+      if (instance.project.vcs === "git") {
+        const currentBranch = async () => {
+          const result = await git(["rev-parse", "--abbrev-ref", "HEAD"], {
+            cwd: instance.project.worktree,
+          })
+          if (result.exitCode !== 0) return undefined
+          const text = result.text().trim()
+          return text || undefined
+        }
+
+        current = yield* Effect.promise(() => currentBranch())
+        log.info("initialized", { branch: current })
+
+        const unsubscribe = Bus.subscribe(
+          FileWatcher.Event.Updated,
+          Instance.bind(async (evt) => {
+            if (!evt.properties.file.endsWith("HEAD")) return
+            const next = await currentBranch()
+            if (next !== current) {
+              log.info("branch changed", { from: current, to: next })
+              current = next
+              Bus.publish(Vcs.Event.BranchUpdated, { branch: next })
+            }
+          }),
+        )
+
+        yield* Effect.addFinalizer(() => Effect.sync(unsubscribe))
+      }
+
+      return VcsService.of({
+        init: Effect.fn("VcsService.init")(function* () {}),
+        branch: Effect.fn("VcsService.branch")(function* () {
+          return current
+        }),
+      })
+    }),
+  )
+}

packages/opencode/src/pty/index.ts

@@ -167,40 +167,44 @@ export namespace Pty {
       subscribers: new Map(),
     }
     state().set(id, session)
-    ptyProcess.onData((chunk) => {
-      session.cursor += chunk.length
+    ptyProcess.onData(
+      Instance.bind((chunk) => {
+        session.cursor += chunk.length
 
-      for (const [key, ws] of session.subscribers.entries()) {
-        if (ws.readyState !== 1) {
-          session.subscribers.delete(key)
-          continue
+        for (const [key, ws] of session.subscribers.entries()) {
+          if (ws.readyState !== 1) {
+            session.subscribers.delete(key)
+            continue
+          }
+
+          if (ws.data !== key) {
+            session.subscribers.delete(key)
+            continue
+          }
+
+          try {
+            ws.send(chunk)
+          } catch {
+            session.subscribers.delete(key)
+          }
         }
 
-        if (ws.data !== key) {
-          session.subscribers.delete(key)
-          continue
-        }
-
-        try {
-          ws.send(chunk)
-        } catch {
-          session.subscribers.delete(key)
-        }
-      }
-
-      session.buffer += chunk
-      if (session.buffer.length <= BUFFER_LIMIT) return
-      const excess = session.buffer.length - BUFFER_LIMIT
-      session.buffer = session.buffer.slice(excess)
-      session.bufferCursor += excess
-    })
-    ptyProcess.onExit(({ exitCode }) => {
-      if (session.info.status === "exited") return
-      log.info("session exited", { id, exitCode })
-      session.info.status = "exited"
-      Bus.publish(Event.Exited, { id, exitCode })
-      remove(id)
-    })
+        session.buffer += chunk
+        if (session.buffer.length <= BUFFER_LIMIT) return
+        const excess = session.buffer.length - BUFFER_LIMIT
+        session.buffer = session.buffer.slice(excess)
+        session.bufferCursor += excess
+      }),
+    )
+    ptyProcess.onExit(
+      Instance.bind(({ exitCode }) => {
+        if (session.info.status === "exited") return
+        log.info("session exited", { id, exitCode })
+        session.info.status = "exited"
+        Bus.publish(Event.Exited, { id, exitCode })
+        remove(id)
+      }),
+    )
     Bus.publish(Event.Created, { info })
     return info
   }

packages/opencode/src/server/server.ts

@@ -14,7 +14,8 @@ import { LSP } from "../lsp"
 import { Format } from "../format"
 import { TuiRoutes } from "./routes/tui"
 import { Instance } from "../project/instance"
-import { Vcs } from "../project/vcs"
+import { Vcs, VcsService } from "../project/vcs"
+import { runPromiseInstance } from "@/effect/runtime"
 import { Agent } from "../agent/agent"
 import { Skill } from "../skill/skill"
 import { Auth } from "../auth"
@@ -330,7 +331,7 @@ export namespace Server {
           },
         }),
         async (c) => {
-          const branch = await Vcs.branch()
+          const branch = await runPromiseInstance(VcsService.use((s) => s.branch()))
           return c.json({
             branch,
           })

packages/opencode/test/file/time.test.ts

@@ -1,361 +1,126 @@
-import { describe, test, expect, beforeEach } from "bun:test"
-import path from "path"
+import { afterEach, expect, test } from "bun:test"
 import fs from "fs/promises"
-import { FileTime } from "../../src/file/time"
-import { Instance } from "../../src/project/instance"
-import { Filesystem } from "../../src/util/filesystem"
+import path from "path"
 import { tmpdir } from "../fixture/fixture"
+import { Instance } from "../../src/project/instance"
+import { FileTime } from "../../src/file/time"
 
-describe("file/time", () => {
-  const sessionID = "test-session-123"
+afterEach(() => Instance.disposeAll())
 
-  describe("read() and get()", () => {
-    test("stores read timestamp", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-      await fs.writeFile(filepath, "content", "utf-8")
+test("read records a timestamp for a file", async () => {
+  await using tmp = await tmpdir()
+  const file = path.join(tmp.path, "test.txt")
+  await fs.writeFile(file, "hello")
 
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          const before = FileTime.get(sessionID, filepath)
-          expect(before).toBeUndefined()
-
-          FileTime.read(sessionID, filepath)
-
-          const after = FileTime.get(sessionID, filepath)
-          expect(after).toBeInstanceOf(Date)
-          expect(after!.getTime()).toBeGreaterThan(0)
-        },
-      })
-    })
-
-    test("tracks separate timestamps per session", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-      await fs.writeFile(filepath, "content", "utf-8")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          FileTime.read("session1", filepath)
-          FileTime.read("session2", filepath)
-
-          const time1 = FileTime.get("session1", filepath)
-          const time2 = FileTime.get("session2", filepath)
-
-          expect(time1).toBeDefined()
-          expect(time2).toBeDefined()
-        },
-      })
-    })
-
-    test("updates timestamp on subsequent reads", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-      await fs.writeFile(filepath, "content", "utf-8")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          FileTime.read(sessionID, filepath)
-          const first = FileTime.get(sessionID, filepath)!
-
-          await new Promise((resolve) => setTimeout(resolve, 10))
-
-          FileTime.read(sessionID, filepath)
-          const second = FileTime.get(sessionID, filepath)!
-
-          expect(second.getTime()).toBeGreaterThanOrEqual(first.getTime())
-        },
-      })
-    })
-  })
-
-  describe("assert()", () => {
-    test("passes when file has not been modified", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-      await fs.writeFile(filepath, "content", "utf-8")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          FileTime.read(sessionID, filepath)
-
-          // Should not throw
-          await FileTime.assert(sessionID, filepath)
-        },
-      })
-    })
-
-    test("throws when file was not read first", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-      await fs.writeFile(filepath, "content", "utf-8")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          await expect(FileTime.assert(sessionID, filepath)).rejects.toThrow("You must read file")
-        },
-      })
-    })
-
-    test("throws when file was modified after read", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-      await fs.writeFile(filepath, "content", "utf-8")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          FileTime.read(sessionID, filepath)
-
-          // Wait to ensure different timestamps
-          await new Promise((resolve) => setTimeout(resolve, 100))
-
-          // Modify file after reading
-          await fs.writeFile(filepath, "modified content", "utf-8")
-
-          await expect(FileTime.assert(sessionID, filepath)).rejects.toThrow("modified since it was last read")
-        },
-      })
-    })
-
-    test("includes timestamps in error message", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-      await fs.writeFile(filepath, "content", "utf-8")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          FileTime.read(sessionID, filepath)
-          await new Promise((resolve) => setTimeout(resolve, 100))
-          await fs.writeFile(filepath, "modified", "utf-8")
-
-          let error: Error | undefined
-          try {
-            await FileTime.assert(sessionID, filepath)
-          } catch (e) {
-            error = e as Error
-          }
-          expect(error).toBeDefined()
-          expect(error!.message).toContain("Last modification:")
-          expect(error!.message).toContain("Last read:")
-        },
-      })
-    })
-
-    test("skips check when OPENCODE_DISABLE_FILETIME_CHECK is true", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-      await fs.writeFile(filepath, "content", "utf-8")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          const { Flag } = await import("../../src/flag/flag")
-          const original = Flag.OPENCODE_DISABLE_FILETIME_CHECK
-          ;(Flag as { OPENCODE_DISABLE_FILETIME_CHECK: boolean }).OPENCODE_DISABLE_FILETIME_CHECK = true
-
-          try {
-            // Should not throw even though file wasn't read
-            await FileTime.assert(sessionID, filepath)
-          } finally {
-            ;(Flag as { OPENCODE_DISABLE_FILETIME_CHECK: boolean }).OPENCODE_DISABLE_FILETIME_CHECK = original
-          }
-        },
-      })
-    })
-  })
-
-  describe("withLock()", () => {
-    test("executes function within lock", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          let executed = false
-          await FileTime.withLock(filepath, async () => {
-            executed = true
-            return "result"
-          })
-          expect(executed).toBe(true)
-        },
-      })
-    })
-
-    test("returns function result", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          const result = await FileTime.withLock(filepath, async () => {
-            return "success"
-          })
-          expect(result).toBe("success")
-        },
-      })
-    })
-
-    test("serializes concurrent operations on same file", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          const order: number[] = []
-
-          const op1 = FileTime.withLock(filepath, async () => {
-            order.push(1)
-            await new Promise((resolve) => setTimeout(resolve, 10))
-            order.push(2)
-          })
-
-          const op2 = FileTime.withLock(filepath, async () => {
-            order.push(3)
-            order.push(4)
-          })
-
-          await Promise.all([op1, op2])
-
-          // Operations should be serialized
-          expect(order).toContain(1)
-          expect(order).toContain(2)
-          expect(order).toContain(3)
-          expect(order).toContain(4)
-        },
-      })
-    })
-
-    test("allows concurrent operations on different files", async () => {
-      await using tmp = await tmpdir()
-      const filepath1 = path.join(tmp.path, "file1.txt")
-      const filepath2 = path.join(tmp.path, "file2.txt")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          let started1 = false
-          let started2 = false
-
-          const op1 = FileTime.withLock(filepath1, async () => {
-            started1 = true
-            await new Promise((resolve) => setTimeout(resolve, 50))
-            expect(started2).toBe(true) // op2 should have started while op1 is running
-          })
-
-          const op2 = FileTime.withLock(filepath2, async () => {
-            started2 = true
-          })
-
-          await Promise.all([op1, op2])
-
-          expect(started1).toBe(true)
-          expect(started2).toBe(true)
-        },
-      })
-    })
-
-    test("releases lock even if function throws", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          await expect(
-            FileTime.withLock(filepath, async () => {
-              throw new Error("Test error")
-            }),
-          ).rejects.toThrow("Test error")
-
-          // Lock should be released, subsequent operations should work
-          let executed = false
-          await FileTime.withLock(filepath, async () => {
-            executed = true
-          })
-          expect(executed).toBe(true)
-        },
-      })
-    })
-
-    test("deadlocks on nested locks (expected behavior)", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          // Nested locks on same file cause deadlock - this is expected
-          // The outer lock waits for inner to complete, but inner waits for outer to release
-          const timeout = new Promise<never>((_, reject) =>
-            setTimeout(() => reject(new Error("Deadlock detected")), 100),
-          )
-
-          const nestedLock = FileTime.withLock(filepath, async () => {
-            return FileTime.withLock(filepath, async () => {
-              return "inner"
-            })
-          })
-
-          // Should timeout due to deadlock
-          await expect(Promise.race([nestedLock, timeout])).rejects.toThrow("Deadlock detected")
-        },
-      })
-    })
-  })
-
-  describe("stat() Filesystem.stat pattern", () => {
-    test("reads file modification time via Filesystem.stat()", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-      await fs.writeFile(filepath, "content", "utf-8")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          FileTime.read(sessionID, filepath)
-
-          const stats = Filesystem.stat(filepath)
-          expect(stats?.mtime).toBeInstanceOf(Date)
-          expect(stats!.mtime.getTime()).toBeGreaterThan(0)
-
-          // FileTime.assert uses this stat internally
-          await FileTime.assert(sessionID, filepath)
-        },
-      })
-    })
-
-    test("detects modification via stat mtime", async () => {
-      await using tmp = await tmpdir()
-      const filepath = path.join(tmp.path, "file.txt")
-      await fs.writeFile(filepath, "original", "utf-8")
-
-      await Instance.provide({
-        directory: tmp.path,
-        fn: async () => {
-          FileTime.read(sessionID, filepath)
-
-          const originalStat = Filesystem.stat(filepath)
-
-          // Wait and modify
-          await new Promise((resolve) => setTimeout(resolve, 100))
-          await fs.writeFile(filepath, "modified", "utf-8")
-
-          const newStat = Filesystem.stat(filepath)
-          expect(newStat!.mtime.getTime()).toBeGreaterThan(originalStat!.mtime.getTime())
-
-          await expect(FileTime.assert(sessionID, filepath)).rejects.toThrow()
-        },
-      })
-    })
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      const before = new Date()
+      FileTime.read("session-1", file)
+      // read is fire-and-forget async — wait a tick for it to complete
+      await Bun.sleep(10)
+      const time = await FileTime.get("session-1", file)
+      expect(time).toBeDefined()
+      expect(time!.getTime()).toBeGreaterThanOrEqual(before.getTime())
+    },
+  })
+})
+
+test("get returns undefined for unread files", async () => {
+  await using tmp = await tmpdir()
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      const time = await FileTime.get("session-1", "/nonexistent")
+      expect(time).toBeUndefined()
+    },
+  })
+})
+
+test("read times are scoped per session", async () => {
+  await using tmp = await tmpdir()
+  const file = path.join(tmp.path, "test.txt")
+  await fs.writeFile(file, "hello")
+
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      FileTime.read("session-a", file)
+      await Bun.sleep(10)
+      expect(await FileTime.get("session-a", file)).toBeDefined()
+      expect(await FileTime.get("session-b", file)).toBeUndefined()
+    },
+  })
+})
+
+test("assert throws if file was not read first", async () => {
+  await using tmp = await tmpdir()
+  const file = path.join(tmp.path, "test.txt")
+  await fs.writeFile(file, "hello")
+
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      await expect(FileTime.assert("session-1", file)).rejects.toThrow("must read file")
+    },
+  })
+})
+
+test("assert passes if file unchanged since read", async () => {
+  await using tmp = await tmpdir()
+  const file = path.join(tmp.path, "test.txt")
+  await fs.writeFile(file, "hello")
+
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      FileTime.read("session-1", file)
+      await Bun.sleep(10)
+      await FileTime.assert("session-1", file)
+    },
+  })
+})
+
+test("assert throws if file modified after read", async () => {
+  await using tmp = await tmpdir()
+  const file = path.join(tmp.path, "test.txt")
+  await fs.writeFile(file, "hello")
+
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      FileTime.read("session-1", file)
+      await Bun.sleep(100)
+      await fs.writeFile(file, "modified")
+      await expect(FileTime.assert("session-1", file)).rejects.toThrow("has been modified")
+    },
+  })
+})
+
+test("withLock serializes concurrent writes to same file", async () => {
+  await using tmp = await tmpdir()
+  const file = path.join(tmp.path, "locked.txt")
+  await fs.writeFile(file, "")
+
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      const order: number[] = []
+
+      const a = FileTime.withLock(file, async () => {
+        order.push(1)
+        await Bun.sleep(50)
+        order.push(2)
+      })
+
+      const b = FileTime.withLock(file, async () => {
+        order.push(3)
+        await Bun.sleep(10)
+        order.push(4)
+      })
+
+      await Promise.all([a, b])
+      expect(order).toEqual([1, 2, 3, 4])
+    },
   })
 })

packages/opencode/test/file/watcher.test.ts

@@ -0,0 +1,236 @@
+import { $ } from "bun"
+import { afterEach, describe, expect, test } from "bun:test"
+import fs from "fs/promises"
+import path from "path"
+import { Deferred, Effect, Fiber, Option } from "effect"
+import { tmpdir } from "../fixture/fixture"
+import { watcherConfigLayer, withServices } from "../fixture/instance"
+import { FileWatcher, FileWatcherService } from "../../src/file/watcher"
+import { Instance } from "../../src/project/instance"
+import { GlobalBus } from "../../src/bus/global"
+
+// Native @parcel/watcher bindings aren't reliably available in CI (missing on Linux, flaky on Windows)
+const describeWatcher = FileWatcher.hasNativeBinding() && !process.env.CI ? describe : describe.skip
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+type BusUpdate = { directory?: string; payload: { type: string; properties: WatcherEvent } }
+type WatcherEvent = { file: string; event: "add" | "change" | "unlink" }
+
+/** Run `body` with a live FileWatcherService. */
+function withWatcher<E>(directory: string, body: Effect.Effect<void, E>) {
+  return withServices(
+    directory,
+    FileWatcherService.layer,
+    async (rt) => {
+      await rt.runPromise(FileWatcherService.use((s) => s.init()))
+      await Effect.runPromise(ready(directory))
+      await Effect.runPromise(body)
+    },
+    { provide: [watcherConfigLayer] },
+  )
+}
+
+function listen(directory: string, check: (evt: WatcherEvent) => boolean, hit: (evt: WatcherEvent) => void) {
+  let done = false
+
+  function on(evt: BusUpdate) {
+    if (done) return
+    if (evt.directory !== directory) return
+    if (evt.payload.type !== FileWatcher.Event.Updated.type) return
+    if (!check(evt.payload.properties)) return
+    hit(evt.payload.properties)
+  }
+
+  function cleanup() {
+    if (done) return
+    done = true
+    GlobalBus.off("event", on)
+  }
+
+  GlobalBus.on("event", on)
+  return cleanup
+}
+
+function wait(directory: string, check: (evt: WatcherEvent) => boolean) {
+  return Effect.callback<WatcherEvent>((resume) => {
+    const cleanup = listen(directory, check, (evt) => {
+      cleanup()
+      resume(Effect.succeed(evt))
+    })
+    return Effect.sync(cleanup)
+  }).pipe(Effect.timeout("5 seconds"))
+}
+
+function nextUpdate<E>(directory: string, check: (evt: WatcherEvent) => boolean, trigger: Effect.Effect<void, E>) {
+  return Effect.acquireUseRelease(
+    wait(directory, check).pipe(Effect.forkChild({ startImmediately: true })),
+    (fiber) =>
+      Effect.gen(function* () {
+        yield* trigger
+        return yield* Fiber.join(fiber)
+      }),
+    Fiber.interrupt,
+  )
+}
+
+/** Effect that asserts no matching event arrives within `ms`. */
+function noUpdate<E>(
+  directory: string,
+  check: (evt: WatcherEvent) => boolean,
+  trigger: Effect.Effect<void, E>,
+  ms = 500,
+) {
+  return Effect.gen(function* () {
+    const deferred = yield* Deferred.make<WatcherEvent>()
+
+    yield* Effect.acquireUseRelease(
+      Effect.sync(() =>
+        listen(directory, check, (evt) => {
+          Effect.runSync(Deferred.succeed(deferred, evt))
+        }),
+      ),
+      () =>
+        Effect.gen(function* () {
+          yield* trigger
+          expect(yield* Deferred.await(deferred).pipe(Effect.timeoutOption(`${ms} millis`))).toEqual(Option.none())
+        }),
+      (cleanup) => Effect.sync(cleanup),
+    )
+  })
+}
+
+function ready(directory: string) {
+  const file = path.join(directory, `.watcher-${Math.random().toString(36).slice(2)}`)
+  const head = path.join(directory, ".git", "HEAD")
+
+  return Effect.gen(function* () {
+    yield* nextUpdate(
+      directory,
+      (evt) => evt.file === file && evt.event === "add",
+      Effect.promise(() => fs.writeFile(file, "ready")),
+    ).pipe(Effect.ensuring(Effect.promise(() => fs.rm(file, { force: true }).catch(() => undefined))), Effect.asVoid)
+
+    const git = yield* Effect.promise(() =>
+      fs
+        .stat(head)
+        .then(() => true)
+        .catch(() => false),
+    )
+    if (!git) return
+
+    const branch = `watch-${Math.random().toString(36).slice(2)}`
+    const hash = yield* Effect.promise(() => $`git rev-parse HEAD`.cwd(directory).quiet().text())
+    yield* nextUpdate(
+      directory,
+      (evt) => evt.file === head && evt.event !== "unlink",
+      Effect.promise(async () => {
+        await fs.writeFile(path.join(directory, ".git", "refs", "heads", branch), hash.trim() + "\n")
+        await fs.writeFile(head, `ref: refs/heads/${branch}\n`)
+      }),
+    ).pipe(Effect.asVoid)
+  })
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+describeWatcher("FileWatcherService", () => {
+  afterEach(() => Instance.disposeAll())
+
+  test("publishes root create, update, and delete events", async () => {
+    await using tmp = await tmpdir({ git: true })
+    const file = path.join(tmp.path, "watch.txt")
+    const dir = tmp.path
+    const cases = [
+      { event: "add" as const, trigger: Effect.promise(() => fs.writeFile(file, "a")) },
+      { event: "change" as const, trigger: Effect.promise(() => fs.writeFile(file, "b")) },
+      { event: "unlink" as const, trigger: Effect.promise(() => fs.unlink(file)) },
+    ]
+
+    await withWatcher(
+      dir,
+      Effect.forEach(cases, ({ event, trigger }) =>
+        nextUpdate(dir, (evt) => evt.file === file && evt.event === event, trigger).pipe(
+          Effect.tap((evt) => Effect.sync(() => expect(evt).toEqual({ file, event }))),
+        ),
+      ),
+    )
+  })
+
+  test("watches non-git roots", async () => {
+    await using tmp = await tmpdir()
+    const file = path.join(tmp.path, "plain.txt")
+    const dir = tmp.path
+
+    await withWatcher(
+      dir,
+      nextUpdate(
+        dir,
+        (e) => e.file === file && e.event === "add",
+        Effect.promise(() => fs.writeFile(file, "plain")),
+      ).pipe(Effect.tap((evt) => Effect.sync(() => expect(evt).toEqual({ file, event: "add" })))),
+    )
+  })
+
+  test("cleanup stops publishing events", async () => {
+    await using tmp = await tmpdir({ git: true })
+    const file = path.join(tmp.path, "after-dispose.txt")
+
+    // Start and immediately stop the watcher (withWatcher disposes on exit)
+    await withWatcher(tmp.path, Effect.void)
+
+    // Now write a file — no watcher should be listening
+    await Effect.runPromise(
+      noUpdate(
+        tmp.path,
+        (e) => e.file === file,
+        Effect.promise(() => fs.writeFile(file, "gone")),
+      ),
+    )
+  })
+
+  test("ignores .git/index changes", async () => {
+    await using tmp = await tmpdir({ git: true })
+    const gitIndex = path.join(tmp.path, ".git", "index")
+    const edit = path.join(tmp.path, "tracked.txt")
+
+    await withWatcher(
+      tmp.path,
+      noUpdate(
+        tmp.path,
+        (e) => e.file === gitIndex,
+        Effect.promise(async () => {
+          await fs.writeFile(edit, "a")
+          await $`git add .`.cwd(tmp.path).quiet().nothrow()
+        }),
+      ),
+    )
+  })
+
+  test("publishes .git/HEAD events", async () => {
+    await using tmp = await tmpdir({ git: true })
+    const head = path.join(tmp.path, ".git", "HEAD")
+    const branch = `watch-${Math.random().toString(36).slice(2)}`
+    await $`git branch ${branch}`.cwd(tmp.path).quiet()
+
+    await withWatcher(
+      tmp.path,
+      nextUpdate(
+        tmp.path,
+        (evt) => evt.file === head && evt.event !== "unlink",
+        Effect.promise(() => fs.writeFile(head, `ref: refs/heads/${branch}\n`)),
+      ).pipe(
+        Effect.tap((evt) =>
+          Effect.sync(() => {
+            expect(evt.file).toBe(head)
+            expect(["add", "change"]).toContain(evt.event)
+          }),
+        ),
+      ),
+    )
+  })
+})

packages/opencode/test/fixture/instance.ts

@@ -0,0 +1,47 @@
+import { ConfigProvider, Layer, ManagedRuntime } from "effect"
+import { InstanceContext } from "../../src/effect/instance-context"
+import { Instance } from "../../src/project/instance"
+
+/** ConfigProvider that enables the experimental file watcher. */
+export const watcherConfigLayer = ConfigProvider.layer(
+  ConfigProvider.fromUnknown({
+    OPENCODE_EXPERIMENTAL_FILEWATCHER: "true",
+    OPENCODE_EXPERIMENTAL_DISABLE_FILEWATCHER: "false",
+  }),
+)
+
+/**
+ * Boot an Instance with the given service layers and run `body` with
+ * the ManagedRuntime. Cleanup is automatic — the runtime is disposed
+ * and Instance context is torn down when `body` completes.
+ *
+ * Layers may depend on InstanceContext (provided automatically).
+ * Pass extra layers via `options.provide` (e.g. ConfigProvider.layer).
+ */
+export function withServices<S>(
+  directory: string,
+  layer: Layer.Layer<S, any, InstanceContext>,
+  body: (rt: ManagedRuntime.ManagedRuntime<S, never>) => Promise<void>,
+  options?: { provide?: Layer.Layer<never>[] },
+) {
+  return Instance.provide({
+    directory,
+    fn: async () => {
+      const ctx = Layer.sync(InstanceContext, () =>
+        InstanceContext.of({ directory: Instance.directory, project: Instance.project }),
+      )
+      let resolved: Layer.Layer<S> = Layer.fresh(layer).pipe(Layer.provide(ctx)) as any
+      if (options?.provide) {
+        for (const l of options.provide) {
+          resolved = resolved.pipe(Layer.provide(l)) as any
+        }
+      }
+      const rt = ManagedRuntime.make(resolved)
+      try {
+        await body(rt)
+      } finally {
+        await rt.dispose()
+      }
+    },
+  })
+}

packages/opencode/test/permission/next.test.ts

@@ -977,7 +977,7 @@ test("ask - should deny even when an earlier pattern is ask", async () => {
   await Instance.provide({
     directory: tmp.path,
     fn: async () => {
-      const ask = PermissionNext.ask({
+      const err = await PermissionNext.ask({
         sessionID: SessionID.make("session_test"),
         permission: "bash",
         patterns: ["echo hello", "rm -rf /"],
@@ -987,24 +987,12 @@ test("ask - should deny even when an earlier pattern is ask", async () => {
           { permission: "bash", pattern: "echo *", action: "ask" },
           { permission: "bash", pattern: "rm *", action: "deny" },
         ],
-      })
+      }).then(
+        () => undefined,
+        (err) => err,
+      )
 
-      const out = await Promise.race([
-        ask.then(
-          () => ({ ok: true as const, err: undefined }),
-          (err) => ({ ok: false as const, err }),
-        ),
-        Bun.sleep(100).then(() => "timeout" as const),
-      ])
-
-      if (out === "timeout") {
-        await rejectAll()
-        await ask.catch(() => {})
-        throw new Error("ask timed out instead of denying immediately")
-      }
-
-      expect(out.ok).toBe(false)
-      expect(out.err).toBeInstanceOf(PermissionNext.DeniedError)
+      expect(err).toBeInstanceOf(PermissionNext.DeniedError)
       expect(await PermissionNext.list()).toHaveLength(0)
     },
   })

packages/opencode/test/project/vcs.test.ts

@@ -0,0 +1,117 @@
+import { $ } from "bun"
+import { afterEach, describe, expect, test } from "bun:test"
+import fs from "fs/promises"
+import path from "path"
+import { Layer, ManagedRuntime } from "effect"
+import { tmpdir } from "../fixture/fixture"
+import { watcherConfigLayer, withServices } from "../fixture/instance"
+import { FileWatcher, FileWatcherService } from "../../src/file/watcher"
+import { Instance } from "../../src/project/instance"
+import { GlobalBus } from "../../src/bus/global"
+import { Vcs, VcsService } from "../../src/project/vcs"
+
+// Skip in CI — native @parcel/watcher binding needed
+const describeVcs = FileWatcher.hasNativeBinding() && !process.env.CI ? describe : describe.skip
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+function withVcs(
+  directory: string,
+  body: (rt: ManagedRuntime.ManagedRuntime<FileWatcherService | VcsService, never>) => Promise<void>,
+) {
+  return withServices(
+    directory,
+    Layer.merge(FileWatcherService.layer, VcsService.layer),
+    async (rt) => {
+      await rt.runPromise(FileWatcherService.use((s) => s.init()))
+      await rt.runPromise(VcsService.use((s) => s.init()))
+      await Bun.sleep(200)
+      await body(rt)
+    },
+    { provide: [watcherConfigLayer] },
+  )
+}
+
+type BranchEvent = { directory?: string; payload: { type: string; properties: { branch?: string } } }
+
+/** Wait for a Vcs.Event.BranchUpdated event on GlobalBus */
+function nextBranchUpdate(directory: string, timeout = 5000) {
+  return new Promise<string | undefined>((resolve, reject) => {
+    const timer = setTimeout(() => {
+      GlobalBus.off("event", on)
+      reject(new Error("timed out waiting for BranchUpdated event"))
+    }, timeout)
+
+    function on(evt: BranchEvent) {
+      if (evt.directory !== directory) return
+      if (evt.payload.type !== Vcs.Event.BranchUpdated.type) return
+      clearTimeout(timer)
+      GlobalBus.off("event", on)
+      resolve(evt.payload.properties.branch)
+    }
+
+    GlobalBus.on("event", on)
+  })
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+describeVcs("Vcs", () => {
+  afterEach(() => Instance.disposeAll())
+
+  test("branch() returns current branch name", async () => {
+    await using tmp = await tmpdir({ git: true })
+
+    await withVcs(tmp.path, async (rt) => {
+      const branch = await rt.runPromise(VcsService.use((s) => s.branch()))
+      expect(branch).toBeDefined()
+      expect(typeof branch).toBe("string")
+    })
+  })
+
+  test("branch() returns undefined for non-git directories", async () => {
+    await using tmp = await tmpdir()
+
+    await withVcs(tmp.path, async (rt) => {
+      const branch = await rt.runPromise(VcsService.use((s) => s.branch()))
+      expect(branch).toBeUndefined()
+    })
+  })
+
+  test("publishes BranchUpdated when .git/HEAD changes", async () => {
+    await using tmp = await tmpdir({ git: true })
+    const branch = `test-${Math.random().toString(36).slice(2)}`
+    await $`git branch ${branch}`.cwd(tmp.path).quiet()
+
+    await withVcs(tmp.path, async () => {
+      const pending = nextBranchUpdate(tmp.path)
+
+      const head = path.join(tmp.path, ".git", "HEAD")
+      await fs.writeFile(head, `ref: refs/heads/${branch}\n`)
+
+      const updated = await pending
+      expect(updated).toBe(branch)
+    })
+  })
+
+  test("branch() reflects the new branch after HEAD change", async () => {
+    await using tmp = await tmpdir({ git: true })
+    const branch = `test-${Math.random().toString(36).slice(2)}`
+    await $`git branch ${branch}`.cwd(tmp.path).quiet()
+
+    await withVcs(tmp.path, async (rt) => {
+      const pending = nextBranchUpdate(tmp.path)
+
+      const head = path.join(tmp.path, ".git", "HEAD")
+      await fs.writeFile(head, `ref: refs/heads/${branch}\n`)
+
+      await pending
+      const current = await rt.runPromise(VcsService.use((s) => s.branch()))
+      expect(current).toBe(branch)
+    })
+  })
+})

packages/opencode/test/pty/pty-session.test.ts

@@ -6,7 +6,7 @@ import type { PtyID } from "../../src/pty/schema"
 import { tmpdir } from "../fixture/fixture"
 import { setTimeout as sleep } from "node:timers/promises"
 
-const wait = async (fn: () => boolean, ms = 2000) => {
+const wait = async (fn: () => boolean, ms = 5000) => {
   const end = Date.now() + ms
   while (Date.now() < end) {
     if (fn()) return
@@ -20,7 +20,7 @@ const pick = (log: Array<{ type: "created" | "exited" | "deleted"; id: PtyID }>,
 }
 
 describe("pty", () => {
-  test("publishes created, exited, deleted in order for /bin/ls + remove", async () => {
+  test("publishes created, exited, deleted in order for a short-lived process", async () => {
     if (process.platform === "win32") return
 
     await using dir = await tmpdir({ git: true })
@@ -37,7 +37,11 @@ describe("pty", () => {
 
         let id: PtyID | undefined
         try {
-          const info = await Pty.create({ command: "/bin/ls", title: "ls" })
+          const info = await Pty.create({
+            command: "/usr/bin/env",
+            args: ["sh", "-c", "sleep 0.1"],
+            title: "sleep",
+          })
           id = info.id
 
           await wait(() => pick(log, id!).includes("exited"))