fix(core): move branch watch into Vcs

LocationWatcher only existed to republish git/hg metadata as
filesystem.changed for Vcs. Nothing else consumed those events.
Vcs now owns the Parcel watch, same as skills and config.

packages/core/src/filesystem/location-watcher.ts

@@ -1,77 +0,0 @@
-export * as LocationWatcher from "./location-watcher"
-
-import { makeLocationNode } from "@opencode-ai/util/effect/app-node"
-import { Context, Effect, Layer, Stream } from "effect"
-import { FileSystem } from "@opencode-ai/schema/filesystem"
-import { Document } from "@opencode-ai/schema/config"
-import { Config } from "../config"
-import { Bus } from "../bus"
-import { FSUtil } from "@opencode-ai/util/fs-util"
-import { Git } from "../git"
-import { Location } from "../location"
-import { Watcher } from "./watcher"
-
-export interface Interface {}
-
-export class Service extends Context.Service<Service, Interface>()("@opencode/LocationWatcher") {}
-
-const layer = Layer.effect(
-  Service,
-  Effect.gen(function* () {
-    const location = yield* Location.Service
-    const watcher = yield* Watcher.Service
-    const bus = yield* Bus.Service
-    const fs = yield* FSUtil.Service
-    const git = yield* Git.Service
-    const configService = yield* Config.Service
-    const publish = (update: { type: "create" | "update" | "delete"; path: string }) =>
-      bus.publish(FileSystem.Event.Changed, {
-        file: update.path,
-        event: update.type === "create" ? "add" : update.type === "update" ? "change" : "unlink",
-      })
-
-    yield* Effect.gen(function* () {
-      const config = (yield* configService.entries())
-        .filter((entry): entry is Document => entry.type === "document")
-        .flatMap((item) => item.info.watcher?.ignore ?? [])
-
-      const watch = (dir: string, keep: readonly string[]) =>
-        Effect.gen(function* () {
-          const ignore = (yield* fs.readDirectoryEntries(dir).pipe(Effect.catch(() => Effect.succeed([])))).flatMap(
-            (entry) => (keep.includes(entry.name) ? [] : [entry.name]),
-          )
-          const updates = yield* watcher.subscribe({ path: dir, type: "directory", ignore })
-          yield* updates.pipe(Stream.runForEach(publish), Effect.forkScoped)
-        })
-
-      if (location.vcs?.type === "git") {
-        const resolved = (yield* git.repo.discover(location.directory))?.gitDirectory
-        const vcs = resolved
-          ? yield* fs.realPath(resolved).pipe(Effect.catch(() => Effect.succeed(resolved)))
-          : undefined
-        if (vcs && !config.includes(".git") && !config.includes(vcs) && (!resolved || !config.includes(resolved))) {
-          yield* watch(vcs, ["HEAD", "HEAD.lock"])
-        }
-      }
-      if (location.vcs?.type === "hg") {
-        const store = location.vcs.store
-        const vcs = yield* fs.realPath(store).pipe(Effect.catch(() => Effect.succeed(store)))
-        if (!config.includes(".hg") && !config.includes(vcs)) {
-          yield* watch(vcs, ["branch"])
-        }
-      }
-    }).pipe(
-      Effect.withSpan("LocationWatcher.start", { attributes: { directory: location.directory } }),
-      Effect.catchCause((cause) => Effect.logError("failed to init location watcher service", { cause })),
-      Effect.forkScoped,
-    )
-
-    return Service.of({})
-  }),
-)
-
-export const node = makeLocationNode({
-  service: Service,
-  layer,
-  deps: [Watcher.node, FSUtil.node, Location.node, Config.node, Git.node, Bus.node],
-})

packages/core/src/location-services.ts

@@ -15,7 +15,6 @@ import { FileSystemSearch } from "./filesystem/search"
 import { Generate } from "./generate"
 import { Form } from "./form"
 import { Image } from "./image"
-import { LocationWatcher } from "./filesystem/location-watcher"
 import { Integration } from "./integration"
 import { Location } from "./location"
 import { LocationMutation } from "./location-mutation"
@@ -99,8 +98,6 @@ const locationServiceNodes = [
   Snapshot.node,
   SessionRunnerLLM.node,
   Vcs.node,
-  // Start repository watches only after boot-critical filesystem and Git work.
-  LocationWatcher.node,
 ] as const satisfies readonly Node.LocationNode<unknown, unknown>[]
 
 export const locationServices = LayerNode.group<typeof locationServiceNodes>(locationServiceNodes)

packages/core/src/vcs.ts

@@ -3,7 +3,6 @@ export * as Vcs from "./vcs"
 import path from "path"
 import { Context, Effect, Layer, Stream } from "effect"
 import { FileDiff } from "@opencode-ai/schema/file-diff"
-import { FileSystem } from "@opencode-ai/schema/filesystem"
 import { FileStatus, Info, Mode } from "@opencode-ai/schema/vcs"
 import { VcsEvent } from "@opencode-ai/schema/vcs-event"
 import { makeLocationNode } from "@opencode-ai/util/effect/app-node"
@@ -11,6 +10,8 @@ import { FSUtil } from "@opencode-ai/util/fs-util"
 import { Location } from "./location"
 import { AppProcess } from "@opencode-ai/util/process"
 import { Bus } from "./bus"
+import { Git } from "./git"
+import { Watcher } from "./filesystem/watcher"
 import { VcsGit } from "./vcs/git"
 import { VcsHg } from "./vcs/hg"
 
@@ -44,32 +45,36 @@ const layer = Layer.effect(
     const fs = yield* FSUtil.Service
     const location = yield* Location.Service
     const bus = yield* Bus.Service
+    const git = yield* Git.Service
+    const watcher = yield* Watcher.Service
     const impl = adapter(proc, fs, location)
     const vcs = location.vcs
     const state = { info: impl ? yield* impl.info() : ({ branch: {} } satisfies Info) }
 
     if (vcs && impl) {
-      const store = yield* fs.realPath(vcs.store).pipe(Effect.catch(() => Effect.succeed(vcs.store)))
-      const isBranchMetadata =
-        vcs.type === "git"
-          ? (file: string) => {
-              const name = path.basename(file)
-              return (name === "HEAD" || name === "HEAD.lock") && FSUtil.contains(store, file)
-            }
-          : (file: string) => path.resolve(file) === path.join(store, "branch")
-      yield* bus.subscribe(FileSystem.Event.Changed).pipe(
-        Stream.filter((event) => isBranchMetadata(event.data.file)),
-        Stream.runForEach((event) =>
-          Effect.gen(function* () {
-            const next = yield* impl.info()
-            const changed = state.info.branch.current !== next.branch.current
-            state.info = next
-            if (!changed) return
-            yield* bus.publish(VcsEvent.BranchUpdated, { branch: next.branch.current })
-          }).pipe(Effect.withSpan("Vcs.refreshBranch", { attributes: { file: event.data.file } })),
-        ),
-        Effect.forkScoped({ startImmediately: true }),
-      )
+      yield* Effect.gen(function* () {
+        const discovered = vcs.type === "git" ? (yield* git.repo.discover(location.directory))?.gitDirectory : undefined
+        const target = discovered ?? vcs.store
+        const dir = yield* fs.realPath(target).pipe(Effect.catch(() => Effect.succeed(target)))
+        const keep = vcs.type === "git" ? ["HEAD", "HEAD.lock"] : ["branch"]
+        const ignore = (yield* fs.readDirectoryEntries(dir).pipe(Effect.catch(() => Effect.succeed([])))).flatMap(
+          (entry) => (keep.includes(entry.name) ? [] : [entry.name]),
+        )
+        const updates = yield* watcher.subscribe({ path: dir, type: "directory", ignore })
+        yield* updates.pipe(
+          Stream.filter((update) => keep.includes(path.basename(update.path))),
+          Stream.runForEach((update) =>
+            Effect.gen(function* () {
+              const next = yield* impl.info()
+              const changed = state.info.branch.current !== next.branch.current
+              state.info = next
+              if (!changed) return
+              yield* bus.publish(VcsEvent.BranchUpdated, { branch: next.branch.current })
+            }).pipe(Effect.withSpan("Vcs.refreshBranch", { attributes: { file: update.path } })),
+          ),
+          Effect.forkScoped({ startImmediately: true }),
+        )
+      }).pipe(Effect.catchCause((cause) => Effect.logError("failed to watch vcs metadata", { cause })))
     }
 
     return Service.of({
@@ -91,5 +96,5 @@ const layer = Layer.effect(
 export const node = makeLocationNode({
   service: Service,
   layer: layer,
-  deps: [AppProcess.node, FSUtil.node, Location.node, Bus.node],
+  deps: [AppProcess.node, FSUtil.node, Location.node, Bus.node, Git.node, Watcher.node],
 })

packages/core/test/filesystem/watcher.test.ts

@@ -1,28 +1,15 @@
-import { $ } from "bun"
 import { describe, expect } from "bun:test"
-import fs from "fs/promises"
 import path from "path"
-import { Deferred, Duration, Effect, Fiber, Layer, Option, Schedule, Stream } from "effect"
-import { Config } from "@opencode-ai/core/config"
+import { Deferred, Effect, Fiber, Layer, Schedule, Stream } from "effect"
 import { AppNodeBuilder } from "@opencode-ai/core/effect/app-node-builder"
-import { LayerNode } from "@opencode-ai/util/effect/layer-node"
-import { Bus } from "@opencode-ai/core/bus"
 import { FSUtil } from "@opencode-ai/util/fs-util"
-import { LocationWatcher } from "@opencode-ai/core/filesystem/location-watcher"
 import { Watcher } from "@opencode-ai/core/filesystem/watcher"
-import { FileSystem } from "@opencode-ai/schema/filesystem"
-import { Location } from "@opencode-ai/core/location"
-import { AbsolutePath } from "@opencode-ai/core/schema"
-import { location } from "../fixture/location"
 import { tmpdir } from "../fixture/tmpdir"
 import { testEffect } from "../lib/effect"
 
-type WatcherEvent = { file: string; event: "add" | "change" | "unlink" }
 const describeNative = process.env.CI ? describe.skip : describe
 
-const it = testEffect(AppNodeBuilder.build(LayerNode.group([FSUtil.node, Bus.node])))
-
-const configLayer = Config.testLayer()
+const it = testEffect(AppNodeBuilder.build(FSUtil.node))
 
 describe("Watcher.testLayer", () => {
   it.effect("records subscriptions and broadcasts emitted updates through the service", () =>
@@ -40,7 +27,6 @@ describe("Watcher.testLayer", () => {
       yield* test.emit({ type: "update", path: "/root/file.md" })
 
       expect(Array.from(yield* Fiber.join(received))).toEqual([{ type: "update", path: "/root/file.md" }])
-      // subscriptions() reports acquired watches, so paths come back resolved.
       expect(yield* test.subscriptions()).toEqual([{ path: path.resolve("/root"), type: "directory" }])
     }).pipe(Effect.provide(Watcher.testLayer)),
   )
@@ -126,172 +112,20 @@ describe("Watcher lifecycle", () => {
         expect(counts.unsubscribes).toBe(0)
         return consumer
       }).pipe(withNative(native))
-      // Closing the layer scope tears the native subscription down while the
-      // consumer still holds a reference; the consumer's own release as its
-      // stream ends must not tear it down a second time.
       yield* Fiber.join(consumer)
       expect(counts.unsubscribes).toBe(1)
     })
   })
 })
 
-function provide(directory: string, vcs?: Location.Interface["vcs"], watcher?: Layer.Layer<Watcher.Service>) {
-  const locationLayer = Layer.succeed(
-    Location.Service,
-    Location.Service.of(location({ directory: AbsolutePath.make(directory) }, { vcs })),
-  )
-  const built = AppNodeBuilder.build(LocationWatcher.node, [
-    [Config.node, configLayer],
-    [Location.node, locationLayer],
-    ...(watcher ? ([[Watcher.node, watcher]] as const) : []),
-  ])
-  return Effect.provide(built)
-}
-
-function withTmp<A, E, R>(
-  f: (directory: string, vcs?: Location.Interface["vcs"]) => Effect.Effect<A, E, R>,
-  options?: {
-    vcs?: "git" | "hg"
-    init?: (directory: string) => Promise<void>
-    watcher?: Layer.Layer<Watcher.Service>
-  },
-) {
+function withTmp<A, E, R>(f: (directory: string) => Effect.Effect<A, E, R>) {
   return Effect.acquireRelease(
-    Effect.promise(async () => {
-      const tmp = await tmpdir()
-      if (options?.vcs === "hg") {
-        await fs.mkdir(path.join(tmp.path, ".hg"))
-        return { tmp, vcs: { type: "hg" as const, store: AbsolutePath.make(path.join(tmp.path, ".hg")) } }
-      }
-      if (options?.vcs !== "git") return { tmp, vcs: undefined }
-      await $`git init`.cwd(tmp.path).quiet()
-      await $`git config core.fsmonitor false`.cwd(tmp.path).quiet()
-      await $`git config commit.gpgsign false`.cwd(tmp.path).quiet()
-      await $`git config user.email test@opencode.test`.cwd(tmp.path).quiet()
-      await $`git config user.name Test`.cwd(tmp.path).quiet()
-      await $`git commit --allow-empty -m root`.cwd(tmp.path).quiet()
-      await options.init?.(tmp.path)
-      return { tmp, vcs: { type: "git" as const, store: AbsolutePath.make(path.join(tmp.path, ".git")) } }
-    }),
-    ({ tmp }) => Effect.promise(() => tmp[Symbol.asyncDispose]()),
-  ).pipe(Effect.flatMap(({ tmp, vcs }) => f(tmp.path, vcs).pipe(provide(tmp.path, vcs, options?.watcher))))
-}
-
-describe("LocationWatcher subscriptions", () => {
-  it.live("watches only exact Git branch metadata", () => {
-    const subscriptions: Watcher.WatchInput[] = []
-    const watcher = Layer.succeed(
-      Watcher.Service,
-      Watcher.Service.of({
-        subscribe: (input) => Effect.sync(() => subscriptions.push(input)).pipe(Effect.as(Stream.empty)),
-      }),
-    )
-    return withTmp(
-      (directory) =>
-        Effect.gen(function* () {
-          yield* LocationWatcher.Service
-          yield* Effect.sync(() => subscriptions.length).pipe(
-            Effect.filterOrFail((count) => count > 0),
-            Effect.retry(Schedule.spaced("10 millis")),
-          )
-          yield* Effect.sleep("10 millis")
-          expect(subscriptions).toHaveLength(1)
-          const git = subscriptions[0]
-          if (git?.type !== "directory") throw new Error("expected a directory watch")
-          expect(git.path).toBe(path.join(directory, ".git"))
-          expect(git.ignore ?? []).not.toContain("HEAD")
-          expect(git.ignore ?? []).toContain("objects")
-        }),
-      { vcs: "git", watcher },
-    )
-  })
-
-  it.live("watches only exact Hg branch metadata", () => {
-    const subscriptions: Watcher.WatchInput[] = []
-    const watcher = Layer.succeed(
-      Watcher.Service,
-      Watcher.Service.of({
-        subscribe: (input) => Effect.sync(() => subscriptions.push(input)).pipe(Effect.as(Stream.empty)),
-      }),
-    )
-    return withTmp(
-      (directory) =>
-        Effect.gen(function* () {
-          yield* LocationWatcher.Service
-          yield* Effect.sync(() => subscriptions.length).pipe(
-            Effect.filterOrFail((count) => count > 0),
-            Effect.retry(Schedule.spaced("10 millis")),
-          )
-          yield* Effect.sleep("10 millis")
-          expect(subscriptions).toMatchObject([{ path: path.join(directory, ".hg"), type: "directory" }])
-        }),
-      { vcs: "hg", watcher },
-    )
-  })
-})
-
-function wait(check: (event: WatcherEvent) => boolean) {
-  return Effect.gen(function* () {
-    const bus = yield* Bus.Service
-    const deferred = yield* Deferred.make<WatcherEvent>()
-    const fiber = yield* bus.subscribe(FileSystem.Event.Changed).pipe(
-      Stream.runForEach((event) => {
-        if (!check(event.data)) return Effect.void
-        return Deferred.succeed(deferred, event.data).pipe(Effect.asVoid)
-      }),
-      Effect.forkScoped,
-    )
-    yield* Effect.yieldNow
-    return { deferred, fiber }
-  })
-}
-
-function maybeNextUpdate<E>(
-  check: (event: WatcherEvent) => boolean,
-  trigger: Effect.Effect<void, E>,
-  timeout: Duration.Input = "5 seconds",
-) {
-  return Effect.acquireUseRelease(
-    wait(check),
-    ({ deferred }) => trigger.pipe(Effect.andThen(Deferred.await(deferred)), Effect.timeoutOption(timeout)),
-    ({ fiber }) => Fiber.interrupt(fiber),
-  )
-}
-
-function nextUpdate<E>(check: (event: WatcherEvent) => boolean, trigger: Effect.Effect<void, E>) {
-  return Effect.gen(function* () {
-    const result = yield* maybeNextUpdate(check, trigger)
-    if (Option.isSome(result)) return result.value
-    return yield* Effect.fail(new Error("timed out waiting for file watcher update"))
-  })
-}
-
-function eventuallyUpdate<E>(check: (event: WatcherEvent) => boolean, trigger: () => Effect.Effect<void, E>) {
-  return Effect.gen(function* () {
-    while (true) {
-      const result = yield* maybeNextUpdate(check, trigger(), "250 millis")
-      if (Option.isSome(result)) return result.value
-    }
-  }).pipe(
-    Effect.timeoutOrElse({
-      duration: "5 seconds",
-      orElse: () => Effect.fail(new Error("timed out waiting for file watcher readiness")),
-    }),
-  )
-}
-
-function ready(file: string, eventFile = file) {
-  return Effect.gen(function* () {
-    const fs = yield* FSUtil.Service
-    const content = (yield* fs.readFileStringSafe(file)) ?? `ready-${Math.random()}`
-    yield* eventuallyUpdate(
-      (event) => event.file === eventFile,
-      () => fs.writeFileString(file, content),
-    ).pipe(Effect.asVoid)
-  })
+    Effect.promise(() => tmpdir()),
+    (tmp) => Effect.promise(() => tmp[Symbol.asyncDispose]()),
+  ).pipe(Effect.flatMap((tmp) => f(tmp.path)))
 }
 
-describeNative("LocationWatcher", () => {
+describeNative("Watcher", () => {
   it.live("limits file watches to the exact target", () =>
     withTmp((directory) =>
       Effect.gen(function* () {
@@ -338,85 +172,4 @@ describeNative("LocationWatcher", () => {
       }).pipe(Effect.provide(AppNodeBuilder.build(Watcher.node))),
     ),
   )
-
-  it.live("publishes .git/HEAD events", () =>
-    withTmp(
-      (directory) =>
-        Effect.gen(function* () {
-          const fs = yield* FSUtil.Service
-          const head = path.join(directory, ".git", "HEAD")
-          const branch = `watch-${Math.random().toString(36).slice(2)}`
-          yield* ready(head)
-          yield* Effect.promise(() => $`git branch ${branch}`.cwd(directory).quiet())
-          expect(
-            yield* nextUpdate((event) => event.file === head, fs.writeFileString(head, `ref: refs/heads/${branch}\n`)),
-          ).toEqual({ file: head, event: "change" })
-        }),
-      { vcs: "git" },
-    ),
-  )
-
-  it.live("publishes .git/HEAD events from git checkout", () =>
-    withTmp(
-      (directory) =>
-        Effect.gen(function* () {
-          const head = path.join(directory, ".git", "HEAD")
-          const branch = `watch-${Math.random().toString(36).slice(2)}`
-          yield* ready(head)
-          const event = yield* nextUpdate(
-            (item) => path.basename(item.file) === "HEAD" || path.basename(item.file) === "HEAD.lock",
-            Effect.promise(() => $`git checkout -q -b ${branch}`.cwd(directory).quiet()),
-          )
-          expect(["HEAD", "HEAD.lock"]).toContain(path.basename(event.file))
-        }),
-      { vcs: "git" },
-    ),
-  )
-
-  const describeSymlink = process.platform !== "win32" ? describe : describe.skip
-  describeSymlink("symlinked .git", () => {
-    it.live("publishes .git/HEAD events through a symlinked .git directory", () =>
-      withTmp(
-        (directory) =>
-          Effect.gen(function* () {
-            const afs = yield* FSUtil.Service
-            const actual = path.join(directory, "..", `actual_${path.basename(directory)}`)
-            yield* Effect.addFinalizer(() => Effect.promise(() => fs.rm(actual, { recursive: true, force: true })))
-            const head = path.join(directory, ".git", "HEAD")
-            yield* ready(head, path.join(actual, "HEAD"))
-            const branch = `watch-${Math.random().toString(36).slice(2)}`
-            yield* Effect.promise(() => $`git branch ${branch}`.cwd(directory).quiet())
-            expect(
-              yield* nextUpdate(
-                (event) => event.file === path.join(actual, "HEAD"),
-                afs.writeFileString(head, `ref: refs/heads/${branch}\n`),
-              ),
-            ).toEqual({ file: path.join(actual, "HEAD"), event: "change" })
-          }),
-        {
-          vcs: "git",
-          init: async (directory) => {
-            const actual = path.join(directory, "..", `actual_${path.basename(directory)}`)
-            await fs.rename(path.join(directory, ".git"), actual)
-            await fs.symlink(actual, path.join(directory, ".git"))
-          },
-        },
-      ),
-    )
-  })
-
-  it.live("publishes .hg/branch events", () =>
-    withTmp(
-      (directory) =>
-        Effect.gen(function* () {
-          const fs = yield* FSUtil.Service
-          const branch = path.join(directory, ".hg", "branch")
-          yield* ready(branch)
-          expect(
-            yield* nextUpdate((event) => event.file === branch, fs.writeFileString(branch, "feature\n")),
-          ).toMatchObject({ file: branch })
-        }),
-      { vcs: "hg" },
-    ),
-  )
 })

packages/core/test/vcs-hg.test.ts

@@ -8,7 +8,6 @@ import { Bus } from "@opencode-ai/core/bus"
 import { Location } from "@opencode-ai/core/location"
 import { AbsolutePath } from "@opencode-ai/core/schema"
 import { Vcs } from "@opencode-ai/core/vcs"
-import { FileSystem } from "@opencode-ai/schema/filesystem"
 import { VcsEvent } from "@opencode-ai/schema/vcs-event"
 import { location } from "./fixture/location"
 import { tmpdir } from "./fixture/tmpdir"
@@ -42,7 +41,9 @@ const withTmp = <A, E, R>(f: (directory: string) => Effect.Effect<A, E, R>) =>
 
 const withHg = <A, E, R>(f: (directory: string) => Effect.Effect<A, E, R>) =>
   withTmp((directory) =>
-    Effect.promise(() => hg(directory, "init")).pipe(Effect.andThen(f(directory).pipe(provide(directory)))),
+    Effect.promise(() => hg(directory, "init")).pipe(
+      Effect.andThen(f(directory).pipe(provide(directory))),
+    ),
   )
 
 async function hg(directory: string, ...args: string[]) {
@@ -124,13 +125,7 @@ describeHg("Vcs mercurial", () => {
           .subscribe(VcsEvent.BranchUpdated)
           .pipe(Stream.take(1), Stream.runHead, Effect.forkScoped({ startImmediately: true }))
         yield* Effect.promise(() => hg(directory, "branch", "-q", "feature"))
-        expect(yield* vcs.info()).toEqual({ branch: { current: "default", default: "default" } })
-
-        yield* bus.publish(FileSystem.Event.Changed, {
-          file: path.join(directory, ".hg", "branch"),
-          event: "change",
-        })
-        expect(yield* Fiber.join(updated)).toMatchObject({
+        expect(yield* Fiber.join(updated).pipe(Effect.timeout("5 seconds"))).toMatchObject({
           _tag: "Some",
           value: { location: { directory }, data: { branch: "feature" } },
         })

packages/core/test/vcs.test.ts

@@ -8,27 +8,66 @@ import { Bus } from "@opencode-ai/core/bus"
 import { Location } from "@opencode-ai/core/location"
 import { AbsolutePath } from "@opencode-ai/core/schema"
 import { Vcs } from "@opencode-ai/core/vcs"
-import { FileSystem } from "@opencode-ai/schema/filesystem"
+import { Watcher } from "@opencode-ai/core/filesystem/watcher"
 import { VcsEvent } from "@opencode-ai/schema/vcs-event"
 import { location } from "./fixture/location"
 import { tmpdir } from "./fixture/tmpdir"
 import { it } from "./lib/effect"
 
+const describeNative = process.env.CI ? describe.skip : describe
+
+const locationLayer = (directory: string, git?: boolean) =>
+  Layer.succeed(
+    Location.Service,
+    Location.Service.of(
+      location(
+        { directory: AbsolutePath.make(directory) },
+        git ? { vcs: { type: "git", store: AbsolutePath.make(path.join(directory, ".git")) } } : {},
+      ),
+    ),
+  )
+
 const provide = (directory: string, input: { git?: boolean } = {}) =>
+  Effect.provide(
+    LayerNode.compile(LayerNode.group([Vcs.node, Bus.node]), [[Location.node, locationLayer(directory, input.git)]]),
+  )
+
+function fakeWatcher() {
+  const subscriptions: Watcher.WatchInput[] = []
+  const active = new Set<(update: Watcher.Update) => void>()
+  const native = Watcher.Native.of({
+    subscribe: (input) =>
+      Effect.sync(() => {
+        subscriptions.push(
+          input.type === "file"
+            ? { path: input.target, type: "file" }
+            : input.ignore.length > 0
+              ? { path: input.target, type: "directory", ignore: input.ignore }
+              : { path: input.target, type: "directory" },
+        )
+        active.add(input.publish)
+        return {
+          unsubscribe: () => {
+            active.delete(input.publish)
+            return Promise.resolve()
+          },
+        }
+      }),
+  })
+  return {
+    subscriptions: () => [...subscriptions],
+    emit: (update: Watcher.Update) => {
+      for (const publish of active) publish(update)
+    },
+    layer: Watcher.layer().pipe(Layer.provide(Layer.succeed(Watcher.Native, native))),
+  }
+}
+
+const provideFake = (directory: string, fake: ReturnType<typeof fakeWatcher>, git = true) =>
   Effect.provide(
     LayerNode.compile(LayerNode.group([Vcs.node, Bus.node]), [
-      [
-        Location.node,
-        Layer.succeed(
-          Location.Service,
-          Location.Service.of(
-            location(
-              { directory: AbsolutePath.make(directory) },
-              input.git ? { vcs: { type: "git", store: AbsolutePath.make(path.join(directory, ".git")) } } : {},
-            ),
-          ),
-        ),
-      ],
+      [Location.node, locationLayer(directory, git)],
+      [Watcher.node, fake.layer],
     ]),
   )
 
@@ -93,38 +132,84 @@ describe("Vcs", () => {
     ),
   )
 
-  it.live("caches branch info and publishes HEAD changes", () =>
-    withGit((directory) =>
-      Effect.gen(function* () {
-        yield* Effect.promise(async () => {
-          await fs.writeFile(path.join(directory, "file.txt"), "one\n")
-          await commitAll(directory, "initial")
-        })
-        const vcs = yield* Vcs.Service
-        const bus = yield* Bus.Service
-        expect(yield* vcs.info()).toEqual({ branch: { current: "main", default: undefined } })
+  it.live("watches git branch metadata", () =>
+    withTmp((directory) => {
+      const fake = fakeWatcher()
+      return Effect.promise(() => initRepo(directory)).pipe(
+        Effect.andThen(
+          Effect.gen(function* () {
+            yield* Vcs.Service
+            expect(fake.subscriptions()).toHaveLength(1)
+            const git = fake.subscriptions()[0]
+            if (git?.type !== "directory") throw new Error("expected a directory watch")
+            expect(git.path).toBe(path.join(directory, ".git"))
+            expect(git.ignore ?? []).not.toContain("HEAD")
+            expect(git.ignore ?? []).toContain("objects")
+          }).pipe(provideFake(directory, fake)),
+        ),
+      )
+    }),
+  )
 
-        const updated = yield* bus
-          .subscribe(VcsEvent.BranchUpdated)
-          .pipe(Stream.take(1), Stream.runHead, Effect.forkScoped({ startImmediately: true }))
-        yield* Effect.promise(() => $`git checkout -q -b feature`.cwd(directory).quiet())
+  it.live("caches branch info and publishes HEAD changes", () =>
+    withTmp((directory) => {
+      const fake = fakeWatcher()
+      return Effect.promise(async () => {
+        await initRepo(directory)
+        await fs.writeFile(path.join(directory, "file.txt"), "one\n")
+        await commitAll(directory, "initial")
+      }).pipe(
+        Effect.andThen(
+          Effect.gen(function* () {
+            const vcs = yield* Vcs.Service
+            const bus = yield* Bus.Service
+            expect(yield* vcs.info()).toMatchObject({ branch: { current: "main" } })
 
-        yield* bus.publish(FileSystem.Event.Changed, { file: path.join(directory, "HEAD"), event: "change" })
-        expect(yield* vcs.info()).toEqual({ branch: { current: "main", default: undefined } })
+            const updated = yield* bus
+              .subscribe(VcsEvent.BranchUpdated)
+              .pipe(Stream.take(1), Stream.runHead, Effect.forkScoped({ startImmediately: true }))
+            yield* Effect.promise(() => $`git checkout -q -b feature`.cwd(directory).quiet())
+            fake.emit({ type: "update", path: path.join(directory, ".git", "index.lock") })
+            expect(yield* vcs.info()).toMatchObject({ branch: { current: "main" } })
 
-        yield* bus.publish(FileSystem.Event.Changed, {
-          file: path.join(directory, ".git", "HEAD.lock"),
-          event: "change",
-        })
-        expect(yield* Fiber.join(updated)).toMatchObject({
-          _tag: "Some",
-          value: { location: { directory }, data: { branch: "feature" } },
-        })
-        expect(yield* vcs.info()).toEqual({ branch: { current: "feature", default: "main" } })
-      }),
-    ),
+            fake.emit({ type: "update", path: path.join(directory, ".git", "HEAD.lock") })
+            expect(yield* Fiber.join(updated)).toMatchObject({
+              _tag: "Some",
+              value: { location: { directory }, data: { branch: "feature" } },
+            })
+            expect(yield* vcs.info()).toMatchObject({ branch: { current: "feature" } })
+          }).pipe(provideFake(directory, fake)),
+        ),
+      )
+    }),
   )
 
+  describeNative("native watches", () => {
+    it.live("publishes branch updates on git checkout", () =>
+      withGit((directory) =>
+        Effect.gen(function* () {
+          yield* Effect.promise(async () => {
+            await fs.writeFile(path.join(directory, "file.txt"), "one\n")
+            await commitAll(directory, "initial")
+          })
+          const vcs = yield* Vcs.Service
+          const bus = yield* Bus.Service
+          expect(yield* vcs.info()).toMatchObject({ branch: { current: "main" } })
+          const updated = yield* bus
+            .subscribe(VcsEvent.BranchUpdated)
+            .pipe(Stream.take(1), Stream.runHead, Effect.forkScoped({ startImmediately: true }))
+          yield* Effect.promise(() => $`git checkout -q -b feature`.cwd(directory).quiet())
+          expect(yield* Fiber.join(updated).pipe(Effect.timeout("5 seconds"))).toMatchObject({
+            _tag: "Some",
+            value: { data: { branch: "feature" } },
+          })
+          expect(yield* vcs.info()).toMatchObject({ branch: { current: "feature" } })
+        }),
+      ),
+      { timeout: 15_000 },
+    )
+  })
+
   it.live("diffs the working copy against HEAD with patches", () =>
     withGit((directory) =>
       Effect.gen(function* () {