diff --git a/packages/core/src/file-mutation.ts b/packages/core/src/file-mutation.ts
index a3c6f519a31..25f30e51e5a 100644
--- a/packages/core/src/file-mutation.ts
+++ b/packages/core/src/file-mutation.ts
@@ -3,6 +3,7 @@ export * as FileMutation from "./file-mutation"
 import { Context, Effect, Layer, Schema } from "effect"
 import { dirname } from "path"
 import { KeyedMutex } from "./effect/keyed-mutex"
+import { LayerNode } from "./effect/layer-node"
 import { FSUtil } from "./fs-util"
 
 export interface Target {
@@ -171,6 +172,8 @@ export const layer = Layer.effect(
   }),
 )
 
+export const node = LayerNode.make(layer, [FSUtil.node])
+
 function splitBom(text: string) {
   const stripped = text.replace(/^\uFEFF+/, "")
   return { bom: stripped.length !== text.length, text: stripped }
diff --git a/packages/core/src/location-mutation.ts b/packages/core/src/location-mutation.ts
index a620c66e31f..d137d581401 100644
--- a/packages/core/src/location-mutation.ts
+++ b/packages/core/src/location-mutation.ts
@@ -2,6 +2,7 @@ export * as LocationMutation from "./location-mutation"
 
 import path from "path"
 import { Context, Effect, Layer, Schema } from "effect"
+import { LayerNode } from "./effect/layer-node"
 import { FSUtil } from "./fs-util"
 import { Location } from "./location"
 
@@ -153,3 +154,5 @@ export const layer = Layer.effect(
 )
 
 export const locationLayer = layer
+
+export const node = (location: LayerNode.Node<Location.Service>) => LayerNode.make(layer, [FSUtil.node, location])
diff --git a/packages/core/test/file-mutation.test.ts b/packages/core/test/file-mutation.test.ts
index ba12d7c13cb..4629c0ec77c 100644
--- a/packages/core/test/file-mutation.test.ts
+++ b/packages/core/test/file-mutation.test.ts
@@ -2,6 +2,7 @@ import fs from "fs/promises"
 import path from "path"
 import { describe, expect } from "bun:test"
 import { Deferred, Effect, Fiber, Layer } from "effect"
+import { LayerNode } from "@opencode-ai/core/effect/layer-node"
 import { FileMutation } from "@opencode-ai/core/file-mutation"
 import { FSUtil } from "@opencode-ai/core/fs-util"
 import { Location } from "@opencode-ai/core/location"
@@ -11,14 +12,16 @@ import { location } from "./fixture/location"
 import { tmpdir } from "./fixture/tmpdir"
 import { it } from "./lib/effect"
 
-function provide(directory: string, filesystem = FSUtil.defaultLayer) {
-  const activeLocation = Layer.succeed(
-    Location.Service,
-    Location.Service.of(location({ directory: AbsolutePath.make(directory) })),
+function provide(directory: string, filesystem?: LayerNode.Replacement<FSUtil.Service>) {
+  const activeLocation = LayerNode.make(
+    Layer.succeed(Location.Service, Location.Service.of(location({ directory: AbsolutePath.make(directory) }))),
+    [],
+  )
+  return Effect.provide(
+    LayerNode.buildLayer(LayerNode.group([LocationMutation.node(activeLocation), FileMutation.node]), {
+      replacements: filesystem ? [filesystem] : [],
+    }),
   )
-  const resolution = LocationMutation.layer.pipe(Layer.provide(filesystem), Layer.provide(activeLocation))
-  const mutation = FileMutation.layer.pipe(Layer.provide(filesystem))
-  return Effect.provide(Layer.mergeAll(resolution, mutation))
 }
 
 function withTmp<A, E, R>(f: (directory: string) => Effect.Effect<A, E, R>) {
@@ -347,17 +350,20 @@ describe("FileMutation", () => {
 })
 
 function instrumentWrites(run: <E>(write: Effect.Effect<void, E>, target: string) => Effect.Effect<void, E>) {
-  return Layer.effect(
-    FSUtil.Service,
-    Effect.gen(function* () {
-      const filesystem = yield* FSUtil.Service
-      return FSUtil.Service.of({
-        ...filesystem,
-        writeWithDirs: (target, content, mode) => run(filesystem.writeWithDirs(target, content, mode), target),
-        writeFile: (target, content, options) => run(filesystem.writeFile(target, content, options), target),
-        writeFileString: (target, content, options) =>
-          run(filesystem.writeFileString(target, content, options), target),
-      })
-    }),
-  ).pipe(Layer.provide(FSUtil.defaultLayer))
+  return LayerNode.replace(
+    FSUtil.node,
+    Layer.effect(
+      FSUtil.Service,
+      Effect.gen(function* () {
+        const filesystem = yield* FSUtil.Service
+        return FSUtil.Service.of({
+          ...filesystem,
+          writeWithDirs: (target, content, mode) => run(filesystem.writeWithDirs(target, content, mode), target),
+          writeFile: (target, content, options) => run(filesystem.writeFile(target, content, options), target),
+          writeFileString: (target, content, options) =>
+            run(filesystem.writeFileString(target, content, options), target),
+        })
+      }),
+    ).pipe(Layer.provide(LayerNode.buildLayer(FSUtil.node))),
+  )
 }