From 721cec7a326f21d572462da65ff06fddf31f5b01 Mon Sep 17 00:00:00 2001
From: Milky2018 <842376130@qq.com>
Date: Thu, 13 Aug 2026 11:37:26 +0800
Subject: [PATCH 1/2] refactor(build): eliminate dedicated output directories

---
 .gitignore                                    |   1 -
 AGENTS.md                                     |   4 +-
 README.md                                     |   4 +-
 cli/build_cmd/build_wbtest.mbt                |  54 ++----
 cli/cef/cef_platform_wbtest.mbt               |  11 +-
 cli/dev/dev_wbtest.mbt                        |  38 ++--
 cli/doctor/doctor_wbtest.mbt                  |  20 +-
 cli/fsutil/fsutil_wbtest.mbt                  |   8 +-
 cli/new/new_project_wbtest.mbt                |  21 +-
 cli/new/templates.generated.mbt               |   6 +-
 cli/new/templates.mbt                         |   6 +-
 cli/new/templates/todo/files/.gitignore.mtpl  |   2 +-
 cli/new/templates/todo/files/README.md.mtpl   |   4 +-
 cli/package/package.mbt                       |  64 +++----
 cli/package/package_macos_dmg_wbtest.mbt      |   4 +-
 cli/package/package_wbtest.mbt                |  76 +++-----
 cli/package/package_windows_wbtest.mbt        |  37 ++--
 config/config_test.mbt                        | 102 ++++------
 config/project_config.mbt                     |   2 +-
 config/project_decode.mbt                     |   2 +-
 .../backend/moon.mod                          |   4 +
 .../project-config-backend-metadata/moon.mod  |   2 +
 e2e/test/app_commands_probe_wbtest.mbt        |   8 +-
 e2e/test/dev_extension_process_wbtest.mbt     | 119 +++++++-----
 e2e/test/dev_extension_scenario_wbtest.mbt    |   8 +-
 e2e/test/orchestration_wbtest.mbt             |  57 +++---
 e2e/test/process_lifecycle_wbtest.mbt         |  26 ++-
 e2e/test/scenario_validation_wbtest.mbt       |  11 +-
 examples/44_project_config/main.mbt           |   6 +-
 .../44_project_config/proton.project.json     |   2 +-
 .../46_asset_sidecar_resources/commands.mbt   |   6 -
 examples/46_asset_sidecar_resources/moon.pkg  |   1 -
 .../47_dev_extension_js/proton.project.json   |   6 +-
 .../app_commands_fixture/app_commands.mbt     |   6 -
 examples/app_commands_fixture/moon.pkg        |   1 -
 examples/e2e_fixtures/asset_sidecar.mbt       |   9 -
 examples/e2e_fixtures/web_contents_view.mbt   |  15 +-
 examples/moon.mod                             |   4 +-
 native/scripts/verify_link_config.mjs         |  17 --
 proton/bootstrap/config_paths_wbtest.mbt      |   2 +-
 proton/bootstrap/config_test.mbt              | 181 +++++++-----------
 proton/bootstrap/moon.pkg                     |   5 +
 proton/bootstrap/proton_project_config.mbt    |   2 +-
 proton/catalog/catalog_test.mbt               | 116 +----------
 .../removed-field.proton.ext.json             |   5 +
 .../self-dependency.proton.ext.json           |   7 +
 .../unsupported-platform.proton.ext.json      |   8 +
 .../proton-ext-module/fs/proton.ext.json      |   8 +
 .../testdata/proton-ext-module/moon.mod       |   7 +
 proton/facade_wbtest.mbt                      |  49 ++---
 proton/moon.pkg                               |   1 +
 proton/native_link_config.mjs                 |  14 +-
 scripts/e2e_scaffold_source_smoke.mjs         |   3 +-
 scripts/macos_package_smoke.mjs               |  14 +-
 scripts/windows_package_smoke.ps1             |   2 +-
 55 files changed, 511 insertions(+), 687 deletions(-)
 create mode 100644 config/testdata/project-config-backend-metadata/backend/moon.mod
 create mode 100644 config/testdata/project-config-backend-metadata/moon.mod
 create mode 100644 proton/catalog/testdata/proton-ext-invalid/removed-field.proton.ext.json
 create mode 100644 proton/catalog/testdata/proton-ext-invalid/self-dependency.proton.ext.json
 create mode 100644 proton/catalog/testdata/proton-ext-invalid/unsupported-platform.proton.ext.json
 create mode 100644 proton/catalog/testdata/proton-ext-module/fs/proton.ext.json
 create mode 100644 proton/catalog/testdata/proton-ext-module/moon.mod

diff --git a/.gitignore b/.gitignore
index fe076fc6..53e2f731 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,5 @@
 # MoonBit build artifacts
 _build/
-target/
 .mooncakes/
 .repos/
 dist/
diff --git a/AGENTS.md b/AGENTS.md
index 9ec7da40..6f6a7e30 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -65,8 +65,8 @@ developer must perform them.
   aligned with the actual examples.
 - `proton/prebuilt/<platform>/`: shipped Proton-only native artifacts. Do not
   put CEF runtime files here.
-- `lib/`, `build/`, `_build/`, `target/`, `native/build*`, `native/dist/`:
-  generated or vendored artifacts.
+- `lib/`, `build/`, `_build/`, `native/build*`, `native/dist/`: generated or
+  vendored artifacts. Packaged application artifacts are written to `dist/`.
 - `.proton/`: generated project runtime cache created by `proton_cli cef setup`.
 
 ## Build And Test
diff --git a/README.md b/README.md
index b32b3dbe..a7af14dd 100644
--- a/README.md
+++ b/README.md
@@ -414,7 +414,7 @@ default targets and output directory:
         "role": "Editor"
       }
     ],
-    "output": "target/proton-dist"
+    "output": "dist"
   }
 }
 ```
@@ -439,7 +439,7 @@ proton_cli package --release
 
 The package command performs a debug build by default. Pass `--release` to use
 MoonBit's release build mode, or `--no-build` to reuse an existing build from
-the selected mode. Package output is written to `target/proton-dist` by default.
+the selected mode. Package output is written to `dist` by default.
 Icons, resources, output targets, signing, notarization, custom URL schemes, and
 macOS document types are configured through `proton.project.json` and package command
 options.
diff --git a/cli/build_cmd/build_wbtest.mbt b/cli/build_cmd/build_wbtest.mbt
index bf4b9742..1bb4dbdf 100644
--- a/cli/build_cmd/build_wbtest.mbt
+++ b/cli/build_cmd/build_wbtest.mbt
@@ -25,9 +25,6 @@ async fn[T] expect_build_config_error(
 
 ///|
 fn ensure_build_test_dir(path : String) -> Unit {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
   @mbfs.create_dir(path) catch {
     _ => ()
   }
@@ -101,9 +98,9 @@ test "parse build args package and config" {
 ///|
 test "parse build args accepts an isolated Moon target directory" {
   let raw = parse_build_args([
-    "--package", "app", "--moon-target-dir", "target/build-app",
+    "--package", "app", "--moon-target-dir", "custom-build",
   ])
-  @debug.assert_eq(raw.moon_target_dir, Some("target/build-app"))
+  @debug.assert_eq(raw.moon_target_dir, Some("custom-build"))
 }
 
 ///|
@@ -146,10 +143,10 @@ test "moon build args prepend an isolated target directory" {
     moon_build_args_with_target_dir(
       "app",
       ["--diagnostic-limit", "80"],
-      Some("target/build-app"),
+      Some("custom-build"),
     ),
     [
-      "--target-dir", "target/build-app", "build", "app", "--diagnostic-limit", "80",
+      "--target-dir", "custom-build", "build", "app", "--diagnostic-limit", "80",
       "--target", "native",
     ],
   )
@@ -157,8 +154,7 @@ test "moon build args prepend an isolated target directory" {
 
 ///|
 async test "frontend path validation reports missing directory" {
-  let root = "target/proton-build-cwd"
-  ensure_build_test_dir(root)
+  let root = @async_fs.tmpdir(prefix="proton-build-cwd-")
   let error = try
     resolve_frontend_path(root, Some("missing"), "npm run build")
   catch {
@@ -172,8 +168,7 @@ async test "frontend path validation reports missing directory" {
 
 ///|
 async test "backend path supports nested directories with spaces" {
-  let root = "target/proton build backend"
-  ensure_build_test_dir(root)
+  let root = @async_fs.tmpdir(prefix="proton-build-backend-")
   ensure_build_test_dir(@fsutil.path_join(root, "nested"))
   ensure_build_test_dir(@fsutil.path_join(root, "nested/backend app"))
   let path = resolve_backend_path(root, Some("nested/backend app"))
@@ -182,8 +177,7 @@ async test "backend path supports nested directories with spaces" {
 
 ///|
 async test "build config discovery prefers package-local proton.project.json" {
-  let root = "target/proton-build-package-config"
-  ensure_build_test_dir(root)
+  let root = @async_fs.tmpdir(prefix="proton-build-config-")
   ensure_build_test_dir(@fsutil.path_join(root, "desktop"))
   let package_config = @fsutil.path_join(
     @fsutil.path_join(root, "desktop"),
@@ -201,9 +195,8 @@ async test "build config discovery prefers package-local proton.project.json" {
 ///|
 async test "resolve path accepts Windows backslash relative input" {
   if @path.sep == '\\' {
-    let dir = "target/proton-build-path"
-    ensure_build_test_dir(dir)
-    let resolved = @fsutil.resolve_path(".", "target\\proton-build-path")
+    let dir = @async_fs.tmpdir(prefix="proton-build-path-")
+    let resolved = @fsutil.resolve_path(".", dir.replace_all(old="/", new="\\"))
     assert_true(resolved.contains(":/") || resolved.contains(":\\"))
     assert_true(@fsutil.path_exists(resolved))
     let absolute = resolved.replace_all(old="/", new="\\")
@@ -213,8 +206,7 @@ async test "resolve path accepts Windows backslash relative input" {
 
 ///|
 async test "project config validation rejects unknown top-level fields" {
-  let dir = "target/proton-build-config"
-  ensure_build_test_dir(dir)
+  let dir = @async_fs.tmpdir(prefix="proton-build-config-")
   let path = @fsutil.path_join(dir, "unknown.proton.project.json")
   write_build_test_file(path, build_config_with("legacy_runtime", true))
   let error = expect_build_config_error(() => read_project_config(path))
@@ -231,8 +223,7 @@ async test "project config validation rejects unknown top-level fields" {
 
 ///|
 async test "project config validation requires window" {
-  let dir = "target/proton-build-config"
-  ensure_build_test_dir(dir)
+  let dir = @async_fs.tmpdir(prefix="proton-build-config-")
   let path = @fsutil.path_join(dir, "missing-window.proton.project.json")
   write_build_test_file(
     path,
@@ -259,8 +250,7 @@ async test "project config validation requires window" {
 
 ///|
 async test "project config validation rejects unsupported size_hint" {
-  let dir = "target/proton-build-config"
-  ensure_build_test_dir(dir)
+  let dir = @async_fs.tmpdir(prefix="proton-build-config-")
   let path = @fsutil.path_join(dir, "bad-size-hint.proton.project.json")
   write_build_test_file(
     path,
@@ -294,8 +284,7 @@ async test "project config validation rejects unsupported size_hint" {
 
 ///|
 async test "project config parsing keeps active bundle metadata out of build validation" {
-  let dir = "target/proton-build-config"
-  ensure_build_test_dir(dir)
+  let dir = @async_fs.tmpdir(prefix="proton-build-config-")
   let path = @fsutil.path_join(dir, "active-bundle.proton.project.json")
   write_build_test_file(path, build_config_with("bundle", { "active": true }))
   ignore(read_project_config(path))
@@ -303,9 +292,10 @@ async test "project config parsing keeps active bundle metadata out of build val
 
 ///|
 async test "production entry validation requires file-backed entry" {
+  let dir = @async_fs.tmpdir(prefix="proton-build-entry-")
   let error = try
     validate_production_entry_file(
-      @proton_config.ProjectEntry::Asset("target/proton-build-missing.html"),
+      @proton_config.ProjectEntry::Asset(@fsutil.path_join(dir, "missing.html")),
     )
   catch {
     BuildPathError::Missing(..) as error => error.message()
@@ -314,8 +304,6 @@ async test "production entry validation requires file-backed entry" {
     _ => fail("expected build error")
   }
   assert_true(error.contains("production entry does not exist"))
-  let dir = "target/proton-build-entry"
-  ensure_build_test_dir(dir)
   let file = @fsutil.path_join(dir, "index.html")
   @mbfs.write_string_to_file(file, "<!doctype html>", encoding="utf8") catch {
     err => abort(@debug.render(Repr(err)))
@@ -325,8 +313,7 @@ async test "production entry validation requires file-backed entry" {
 
 ///|
 async test "release validation checks secondary window entry files" {
-  let dir = "target/proton-build-secondary-entry"
-  ensure_build_test_dir(dir)
+  let dir = @async_fs.tmpdir(prefix="proton-build-secondary-")
   let main = @fsutil.path_join(dir, "main.html")
   let missing = @fsutil.path_join(dir, "secondary/missing.html")
   write_build_test_file(main, "<!doctype html>")
@@ -354,7 +341,7 @@ async test "release validation checks secondary window entry files" {
 test "frontend release rejects url production entry" {
   let frontend = Some(
     @proton_config.ProjectFrontendConfig::new(
-      dist=Some("target/proton-build-entry"),
+      dist=Some("fixtures/frontend-dist"),
     ),
   )
   let error = expect_build_error_message(() => {
@@ -374,7 +361,7 @@ test "frontend release config preflight rejects url entry" {
     backend: None,
     frontend: Some(
       @proton_config.ProjectFrontendConfig::new(
-        dist=Some("target/proton-build-entry"),
+        dist=Some("fixtures/frontend-dist"),
       ),
     ),
   }
@@ -387,7 +374,7 @@ test "frontend release requires dist" {
   let config = BuildProjectConfig::{
     base_dir: ".",
     entries: [
-      @proton_config.ProjectEntry::Asset("target/proton-build-entry/index.html"),
+      @proton_config.ProjectEntry::Asset("fixtures/frontend-dist/index.html"),
     ],
     backend: None,
     frontend: Some(
@@ -402,8 +389,7 @@ test "frontend release requires dist" {
 
 ///|
 async test "production entry validation rejects directories" {
-  let dir = "target/proton-build-entry-dir"
-  ensure_build_test_dir(dir)
+  let dir = @async_fs.tmpdir(prefix="proton-build-entry-dir-")
   let error = try
     validate_production_entry_file(@proton_config.ProjectEntry::Asset(dir))
   catch {
diff --git a/cli/cef/cef_platform_wbtest.mbt b/cli/cef/cef_platform_wbtest.mbt
index 7cde5bf7..4f31db73 100644
--- a/cli/cef/cef_platform_wbtest.mbt
+++ b/cli/cef/cef_platform_wbtest.mbt
@@ -75,7 +75,7 @@ test "runtime manifests separate portable and active metadata" {
 
 ///|
 test "CEF cache paths are absolute and scoped by platform and archive" {
-  let project_root = @fsutil.resolve_path(".", "target/proton-cache-project")
+  let project_root = @fsutil.resolve_path(".", "fixtures/proton-cache-project")
   let home = @fsutil.resolve_path(project_root, "../proton-cache-home")
   let cache_root = resolve_global_cef_cache_root(
     project_root~,
@@ -97,7 +97,7 @@ test "CEF cache paths are absolute and scoped by platform and archive" {
 
 ///|
 test "relative CEF cache overrides resolve from the project root" {
-  let project_root = @fsutil.resolve_path(".", "target/proton-cache-project")
+  let project_root = @fsutil.resolve_path(".", "fixtures/proton-cache-project")
   let actual = resolve_global_cef_cache_root(
     project_root~,
     configured_root=Some("../shared-cef"),
@@ -116,10 +116,9 @@ test "relative CEF cache overrides resolve from the project root" {
 
 ///|
 async test "runtime metadata does not persist the active CEF cache path" {
-  let root = @fsutil.resolve_path(".", "target/proton-runtime-manifest")
+  let root = @async_fs.tmpdir(prefix="proton-runtime-manifest-")
   let proton_dir = @fsutil.path_join(root, ".proton")
   let runtime_dir = @fsutil.path_join(proton_dir, "runtime")
-  remove_tree(root)
   ensure_dir(runtime_dir)
   let cef_root = @fsutil.resolve_path(
     root, "../shared-cef/darwin-arm64/cef-test",
@@ -306,8 +305,8 @@ test "generated runtime directories must stay under the project root" {
 
 ///|
 test "CEF installation never removes a project boundary or filesystem root" {
-  let root = @fsutil.resolve_path(".", "target/proton-cef-project")
-  let cache = @fsutil.resolve_path(".", "target/proton-cef-cache/runtime")
+  let root = @fsutil.resolve_path(".", "fixtures/proton-cef-project")
+  let cache = @fsutil.resolve_path(".", "fixtures/proton-cef-cache/runtime")
   assert_safe_install_dir(cache, root)
   let parent = @fsutil.path_parent(root)
   let mut filesystem_root = root
diff --git a/cli/dev/dev_wbtest.mbt b/cli/dev/dev_wbtest.mbt
index 451834e6..6c807d22 100644
--- a/cli/dev/dev_wbtest.mbt
+++ b/cli/dev/dev_wbtest.mbt
@@ -5,9 +5,6 @@ fn parse_dev_args(args : Array[String]) -> RawDevOptions raise {
 
 ///|
 fn ensure_dev_test_dir(path : String) -> Unit {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
   @mbfs.create_dir(path) catch {
     _ => ()
   }
@@ -79,15 +76,14 @@ test "parse dev args package and frontend overrides" {
 ///|
 test "parse dev args accepts an isolated Moon target directory" {
   let raw = parse_dev_args([
-    "--package", "desktop", "--moon-target-dir", "target/dev-app",
+    "--package", "desktop", "--moon-target-dir", "custom-dev-build",
   ])
-  @debug.assert_eq(raw.moon_target_dir, Some("target/dev-app"))
+  @debug.assert_eq(raw.moon_target_dir, Some("custom-dev-build"))
 }
 
 ///|
 async test "read dev project config extracts module paths" {
-  let dir = "target/proton-dev-config"
-  ensure_dev_test_dir(dir)
+  let dir = @async_fs.tmpdir(prefix="proton-dev-config-")
   let path = @fsutil.path_join(dir, "proton.project.json")
   @mbfs.write_string_to_file(
     path,
@@ -129,8 +125,7 @@ async test "read dev project config extracts module paths" {
 
 ///|
 async test "read dev frontend config validates full project config" {
-  let dir = "target/proton-dev-config"
-  ensure_dev_test_dir(dir)
+  let dir = @async_fs.tmpdir(prefix="proton-dev-config-")
   let path = @fsutil.path_join(dir, "bad-size-hint.proton.project.json")
   @mbfs.write_string_to_file(
     path,
@@ -171,8 +166,7 @@ async test "read dev frontend config validates full project config" {
 
 ///|
 async test "frontend path is validated only when frontend starts" {
-  let root = "target/proton-dev-cwd"
-  ensure_dev_test_dir(root)
+  let root = @async_fs.tmpdir(prefix="proton-dev-cwd-")
   ensure_dev_test_dir(@fsutil.path_join(root, "frontend"))
   let resolved = resolve_frontend_path(
     root,
@@ -206,8 +200,7 @@ async test "frontend path is validated only when frontend starts" {
 
 ///|
 async test "dev config discovery prefers package-local proton.project.json" {
-  let root = "target/proton-dev-package-config"
-  ensure_dev_test_dir(root)
+  let root = @async_fs.tmpdir(prefix="proton-dev-config-")
   ensure_dev_test_dir(@fsutil.path_join(root, "desktop"))
   let package_config = @fsutil.path_join(
     @fsutil.path_join(root, "desktop"),
@@ -226,9 +219,8 @@ async test "dev config discovery prefers package-local proton.project.json" {
 
 ///|
 async test "backend path supports nested directories with spaces" {
-  let root = "target/proton dev backend"
+  let root = @async_fs.tmpdir(prefix="proton-dev-backend-")
   let backend = @fsutil.path_join(root, "modules/backend app")
-  ensure_dev_test_dir(root)
   ensure_dev_test_dir(@fsutil.path_join(root, "modules"))
   ensure_dev_test_dir(backend)
   let resolved = resolve_backend_path(root, Some("modules/backend app"))
@@ -237,7 +229,7 @@ async test "backend path supports nested directories with spaces" {
 
 ///|
 async test "dev runtime layout validates helper" {
-  let root = "target/proton-dev-runtime-layout"
+  let root = @async_fs.tmpdir(prefix="proton-dev-runtime-")
   let runtime = create_fake_dev_runtime(root)
   let loaded = dev_runtime_from_root(
     @fsutil.resolve_path(".", runtime),
@@ -277,7 +269,7 @@ async test "dev runtime layout validates helper" {
 
 ///|
 async test "dev process preloads an indirect Linux CEF runtime" {
-  let root = "target/proton-dev-runtime-preload"
+  let root = @async_fs.tmpdir(prefix="proton-dev-preload-")
   let runtime_path = create_fake_dev_runtime(root)
   let runtime = dev_runtime_from_root(
     @fsutil.resolve_path(".", runtime_path),
@@ -377,7 +369,7 @@ test "dev app spawn env replaces inherited Windows variable spellings" {
 
 ///|
 async test "read dev runtime honors PROTON_NATIVE_DIST override" {
-  let root = "target/proton-dev-runtime-env"
+  let root = @async_fs.tmpdir(prefix="proton-dev-runtime-env-")
   let runtime = create_fake_dev_runtime(root)
   let previous = @env.get_env_var("PROTON_NATIVE_DIST")
   defer (match previous {
@@ -396,7 +388,7 @@ async test "read dev runtime honors PROTON_NATIVE_DIST override" {
       @fsutil.path_join(loaded.bin_dir, helper_executable_name()),
     ),
   )
-  let bad_root = "target/proton-dev-runtime-bad-env"
+  let bad_root = @fsutil.path_join(root, "bad")
   ensure_dev_test_dir(bad_root)
   @env.set_env_var("PROTON_NATIVE_DIST", "missing-runtime")
   try ensure_dev_runtime(@fsutil.resolve_path(".", bad_root), true) catch {
@@ -413,9 +405,8 @@ async test "read dev runtime honors PROTON_NATIVE_DIST override" {
 ///|
 async test "resolve path accepts Windows backslash relative input" {
   if @path.sep == '\\' {
-    let dir = "target/proton-dev-path"
-    ensure_dev_test_dir(dir)
-    let resolved = @fsutil.resolve_path(".", "target\\proton-dev-path")
+    let dir = @async_fs.tmpdir(prefix="proton-dev-path-")
+    let resolved = @fsutil.resolve_path(".", dir.replace_all(old="/", new="\\"))
     assert_true(resolved.contains(":/") || resolved.contains(":\\"))
     assert_true(@fsutil.path_exists(resolved))
     let absolute = resolved.replace_all(old="/", new="\\")
@@ -510,8 +501,7 @@ async test "ready path validates curl probe availability" {
 ///|
 #cfg(not(platform="windows"))
 async test "frontend cancellation terminates child processes" {
-  let dir = "target/proton-dev-cancel-tree"
-  ensure_dev_test_dir(dir)
+  let dir = @async_fs.tmpdir(prefix="proton-dev-cancel-")
   let pid_path = @fsutil.path_join(dir, "child.pid")
   @mbfs.remove_file(pid_path) catch {
     _ => ()
diff --git a/cli/doctor/doctor_wbtest.mbt b/cli/doctor/doctor_wbtest.mbt
index 72ba2cf1..315eaf6a 100644
--- a/cli/doctor/doctor_wbtest.mbt
+++ b/cli/doctor/doctor_wbtest.mbt
@@ -1,17 +1,6 @@
-///|
-fn ensure_test_dir(path : String) -> Unit {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.create_dir(path) catch {
-    _ => ()
-  }
-}
-
 ///|
 fn write_test_project(path : String) -> String {
   let root = @path.Path(path).resolve().to_string()
-  ensure_test_dir(root)
   @mbfs.write_string_to_file(
     @fsutil.path_join(root, "proton.project.json"),
     (
@@ -37,7 +26,8 @@ fn write_test_project(path : String) -> String {
 
 ///|
 async test "doctor discovers proton.project.json from a nested directory" {
-  let root = write_test_project("target/proton-doctor-project")
+  let root = @async_fs.tmpdir(prefix="proton-doctor-project-")
+  ignore(write_test_project(root))
   let nested = @fsutil.path_join(root, "nested")
   @mbfs.create_dir(nested) catch {
     _ => ()
@@ -56,8 +46,7 @@ async test "doctor discovers proton.project.json from a nested directory" {
 
 ///|
 async test "doctor skips project checks outside a Proton project" {
-  let root = @path.Path("target/proton-doctor-empty").resolve().to_string()
-  ensure_test_dir(root)
+  let root = @async_fs.tmpdir(prefix="proton-doctor-empty-")
   let report = build_doctor_report(root, verbose=false)
   assert_eq(report.sections.length(), 2)
   assert_false(report.has_errors())
@@ -68,7 +57,8 @@ async test "doctor skips project checks outside a Proton project" {
 
 ///|
 async test "doctor accepts the generated project configuration shape" {
-  let root = write_test_project("target/proton-doctor-valid-config")
+  let root = @async_fs.tmpdir(prefix="proton-doctor-valid-")
+  ignore(write_test_project(root))
   let section = collect_project(discover_project(root))
   assert_true(
     section.lines.any(fn(line) {
diff --git a/cli/fsutil/fsutil_wbtest.mbt b/cli/fsutil/fsutil_wbtest.mbt
index 940189cf..22871105 100644
--- a/cli/fsutil/fsutil_wbtest.mbt
+++ b/cli/fsutil/fsutil_wbtest.mbt
@@ -1,8 +1,5 @@
 ///|
 fn ensure_fsutil_test_dir(path : String) -> Unit {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
   @mbfs.create_dir(path) catch {
     _ => ()
   }
@@ -84,7 +81,7 @@ test "path_parent follows Windows dirname semantics" {
 
 ///|
 test "relative_path and containment use path components" {
-  let root = resolve_path(".", "target/proton-fsutil-containment")
+  let root = resolve_path("/fixture", "proton-fsutil-containment")
   assert_eq(
     relative_path(root, path_join(root, "nested/file")),
     path_join("nested", "file"),
@@ -105,8 +102,7 @@ test "path_join joins with the platform separator" {
 
 ///|
 async test "find_project_root_from walks up to marker" {
-  let root = path_join("target", "proton-fsutil-project-root")
-  ensure_fsutil_test_dir(root)
+  let root = @async_fs.tmpdir(prefix="proton-fsutil-project-root-")
   ensure_fsutil_test_dir(path_join(root, "nested"))
   ensure_fsutil_test_dir(path_join(root, "nested/child"))
   write_fsutil_test_file(path_join(root, "moon.work"), "")
diff --git a/cli/new/new_project_wbtest.mbt b/cli/new/new_project_wbtest.mbt
index 165dfab8..326eea7f 100644
--- a/cli/new/new_project_wbtest.mbt
+++ b/cli/new/new_project_wbtest.mbt
@@ -329,7 +329,7 @@ test "templates receive final author title and size" {
       "bundle": {
         "active": true,
         "targets": ["app", "zip"],
-        "output": "target/proton-dist",
+        "output": "dist",
         ..
       },
       ..
@@ -445,8 +445,9 @@ test "registry dependency failures are classified separately" {
 
 ///|
 async test "project generation commits a complete staged tree" {
+  let workspace = @async_fs.tmpdir(prefix="proton-new-success-")
   let options = transaction_test_options(
-    "target/proton-new-transaction-success",
+    @fsutil.path_join(workspace, "project"),
   )
   remove_new_test_tree(options.resolved_target_dir)
   let files = must_plan(options)
@@ -471,7 +472,10 @@ async test "project generation commits a complete staged tree" {
 
 ///|
 async test "failed project writes leave no target or staging tree" {
-  let options = transaction_test_options("target/proton-new-transaction-failed")
+  let workspace = @async_fs.tmpdir(prefix="proton-new-failed-")
+  let options = transaction_test_options(
+    @fsutil.path_join(workspace, "project"),
+  )
   remove_new_test_tree(options.resolved_target_dir)
   let files = [
     PlannedFile::{ path: "blocked", content: "file" },
@@ -493,8 +497,9 @@ async test "failed project writes leave no target or staging tree" {
 
 ///|
 async test "failed project writes restore an existing empty target" {
+  let workspace = @async_fs.tmpdir(prefix="proton-new-empty-")
   let options = transaction_test_options(
-    "target/proton-new-transaction-empty-target",
+    @fsutil.path_join(workspace, "project"),
   )
   remove_new_test_tree(options.resolved_target_dir)
   ensure_dir_recursive(options.resolved_target_dir)
@@ -515,8 +520,9 @@ async test "failed project writes restore an existing empty target" {
 
 ///|
 async test "cancelled project generation removes its staging tree" {
+  let workspace = @async_fs.tmpdir(prefix="proton-new-cancelled-")
   let options = transaction_test_options(
-    "target/proton-new-transaction-cancelled",
+    @fsutil.path_join(workspace, "project"),
   )
   remove_new_test_tree(options.resolved_target_dir)
   let outcome = @async.with_timeout_opt(0, () => {
@@ -533,8 +539,11 @@ async test "cancelled project generation removes its staging tree" {
 
 ///|
 async test "moon check failure is rolled back before publication" {
+  let workspace = @async_fs.tmpdir(prefix="proton-new-check-failed-")
   let raw = must_parse([
-    "target/proton-new-transaction-check-failed", "--check", "--no-git",
+    @fsutil.path_join(workspace, "project"),
+    "--check",
+    "--no-git",
   ])
   let options = options_from_raw(".", raw)
   remove_new_test_tree(options.resolved_target_dir)
diff --git a/cli/new/templates.generated.mbt b/cli/new/templates.generated.mbt
index 753f9f06..b974015e 100644
--- a/cli/new/templates.generated.mbt
+++ b/cli/new/templates.generated.mbt
@@ -798,7 +798,7 @@ fn generated_template_specs() -> Array[TemplateSpec] {
           #|  "bundle": {
           #|    "active": true,
           #|    "targets": ["app", "zip"],
-          #|    "output": "target/proton-dist"
+          #|    "output": "dist"
           #|  }
           #|}
           #|```
@@ -819,7 +819,7 @@ fn generated_template_specs() -> Array[TemplateSpec] {
           #|  prebuild rule. Ordinary `moon check`, `build`, and `run` commands keep it
           #|  current through `moonx moonbit-community/proton_codegen`.
           #|- `backend/app/main.mbt` assembles and runs the application.
-          #|- `target/proton-dist/` contains packaged application artifacts.
+          #|- `dist/` contains packaged application artifacts.
           #|
       ),
     },
@@ -829,7 +829,7 @@ fn generated_template_specs() -> Array[TemplateSpec] {
       template_source: (
           #|.DS_Store
           #|_build/
-          #|target
+          #|dist/
           #|.mooncakes/
           #|.moonagent/
           #|.proton/
diff --git a/cli/new/templates.mbt b/cli/new/templates.mbt
index b572cb39..14a7c1f1 100644
--- a/cli/new/templates.mbt
+++ b/cli/new/templates.mbt
@@ -231,11 +231,7 @@ fn project_config_file(context : TemplateContext) -> PlannedFile {
     "entry": { "kind": "asset", "value": "frontend/dist/index.html" },
     "permissions": [{ "window": "main", "origin": "entry", "extension": "app" }],
     "debug": true,
-    "bundle": {
-      "active": true,
-      "targets": ["app", "zip"],
-      "output": "target/proton-dist",
-    },
+    "bundle": { "active": true, "targets": ["app", "zip"], "output": "dist" },
   }
   { path: "proton.project.json", content: config.stringify(indent=2) + "\n" }
 }
diff --git a/cli/new/templates/todo/files/.gitignore.mtpl b/cli/new/templates/todo/files/.gitignore.mtpl
index a5384d7f..902ed5f0 100644
--- a/cli/new/templates/todo/files/.gitignore.mtpl
+++ b/cli/new/templates/todo/files/.gitignore.mtpl
@@ -1,6 +1,6 @@
 .DS_Store
 _build/
-target
+dist/
 .mooncakes/
 .moonagent/
 .proton/
diff --git a/cli/new/templates/todo/files/README.md.mtpl b/cli/new/templates/todo/files/README.md.mtpl
index f0ec246c..978f8a21 100644
--- a/cli/new/templates/todo/files/README.md.mtpl
+++ b/cli/new/templates/todo/files/README.md.mtpl
@@ -51,7 +51,7 @@ The `bundle` block in `proton.project.json` controls package creation:
   "bundle": {
     "active": true,
     "targets": ["app", "zip"],
-    "output": "target/proton-dist"
+    "output": "dist"
   }
 }
 ```
@@ -72,4 +72,4 @@ proton_cli package --release
   prebuild rule. Ordinary `moon check`, `build`, and `run` commands keep it
   current through `moonx moonbit-community/proton_codegen`.
 - `backend/app/main.mbt` assembles and runs the application.
-- `target/proton-dist/` contains packaged application artifacts.
+- `dist/` contains packaged application artifacts.
diff --git a/cli/package/package.mbt b/cli/package/package.mbt
index 356b8fe3..42b93288 100644
--- a/cli/package/package.mbt
+++ b/cli/package/package.mbt
@@ -21,7 +21,6 @@ struct RawPackageOptions {
 struct PackagePlan {
   root : String
   workspace_root : String
-  build_target_dir : String
   app_package : String
   config_path : String
   product_name : String
@@ -382,7 +381,6 @@ async fn build_package_plan(
   PackagePlan::{
     root: backend_root,
     workspace_root,
-    build_target_dir: package_build_target_dir(workspace_root, identifier),
     app_package,
     config_path,
     product_name,
@@ -581,7 +579,6 @@ fn print_package_plan(plan : PackagePlan, dry_run : Bool) -> Unit {
   println("  update revision: " + plan.update_revision.to_string())
   println("  targets: " + plan.targets.join(", "))
   println("  output: " + plan.output)
-  println("  build target: " + plan.build_target_dir)
   let sign_binaries = if plan.sign_binaries.length() == 0 {
     "none"
   } else {
@@ -616,7 +613,7 @@ async fn execute_package_plan(plan : PackagePlan) -> Unit {
   let executable = match find_package_executable(plan) {
     Some(path) => path
     None =>
-      raise PackagePlanError::MissingExecutable(path=plan.build_target_dir)
+      raise PackagePlanError::MissingExecutable(path=package_build_root(plan))
   }
   match current_package_host() {
     Windows => stage_windows_portable(plan, executable, runtime)
@@ -638,29 +635,12 @@ async fn run_package_build(plan : PackagePlan) -> Unit {
   if plan.release {
     moon_args.push("--release")
   }
-  moon_args.push("--target-dir")
-  moon_args.push(plan.build_target_dir)
-  let old_rpath = @env.get_env_var("PROTON_PACKAGE_RPATH")
-  // Mach-O only. The link config reads this on darwin; the Linux branch
-  // ignores it and keeps the absolute runtime rpath, which is what a
-  // development run wants. Linux gets its relocatable rpath from patchelf
-  // during staging instead, so `$ORIGIN` never passes through the link
-  // config's quoting.
-  if is_macos_host() {
-    @env.set_env_var(
-      "PROTON_PACKAGE_RPATH", "@executable_path/../Resources/proton/lib",
-    )
-  }
-  defer restore_package_env("PROTON_PACKAGE_RPATH", old_rpath)
   @build.run_release(plan.root, plan.app_package, plan.config_path, moon_args)
 }
 
 ///|
-fn restore_package_env(name : String, value : String?) -> Unit {
-  match value {
-    Some(value) => @env.set_env_var(name, value)
-    None => @env.unset_env_var(name)
-  }
+fn package_build_root(plan : PackagePlan) -> String {
+  @fsutil.resolve_path(plan.workspace_root, "_build")
 }
 
 ///|
@@ -668,7 +648,7 @@ async fn find_package_executable(plan : PackagePlan) -> String? {
   // `--no-build` must reuse the same build mode selected for this command.
   let build_mode = if plan.release { "release" } else { "debug" }
   let root = @fsutil.resolve_path(
-    plan.build_target_dir,
+    package_build_root(plan),
     "native/" + build_mode + "/build",
   )
   let package_name = path_basename(plan.app_package)
@@ -756,17 +736,6 @@ async fn read_active_runtime(root : String) -> String {
   }
 }
 
-///|
-fn package_build_target_dir(
-  workspace_root : String,
-  identifier : String,
-) -> String {
-  @fsutil.resolve_path(
-    workspace_root,
-    "target/proton-package-build/" + package_executable_name(identifier),
-  )
-}
-
 ///|
 async fn require_runtime(path : String) -> String {
   if @fsutil.path_is_dir(path) {
@@ -897,6 +866,11 @@ async fn stage_macos_app_impl(
       )
   }
   require_launchable_macho(staged_executable)
+  replace_macos_rpath(
+    staged_executable,
+    @fsutil.resolve_path(runtime, "lib"),
+    "@executable_path/../Resources/proton/lib",
+  )
   copy_tree(runtime, @fsutil.resolve_path(resources, "proton"))
   stage_release_project_config(
     plan.config_path,
@@ -1619,6 +1593,26 @@ async fn add_macos_rpath(binary : String, rpath : String) -> Unit {
   }
 }
 
+///|
+async fn replace_macos_rpath(
+  binary : String,
+  current : String,
+  replacement : String,
+) -> Unit {
+  let code = @process.run("install_name_tool", [
+    "-rpath", current, replacement, binary,
+  ]) catch {
+    error =>
+      raise PackageToolError::Start(
+        tool="install_name_tool",
+        detail=@debug.render(Repr(error)),
+      )
+  }
+  if code != 0 {
+    raise PackageToolError::Exit(tool="install_name_tool", code~, detail=binary)
+  }
+}
+
 ///|
 fn required_macos_signing_identity() -> String raise MacosSigningError {
   match @env.get_env_var("PROTON_MACOS_SIGNING_IDENTITY") {
diff --git a/cli/package/package_macos_dmg_wbtest.mbt b/cli/package/package_macos_dmg_wbtest.mbt
index cd75ebeb..76e4d0ea 100644
--- a/cli/package/package_macos_dmg_wbtest.mbt
+++ b/cli/package/package_macos_dmg_wbtest.mbt
@@ -4,7 +4,6 @@ fn macos_dmg_test_plan(root : String) -> PackagePlan {
   PackagePlan::{
     root,
     workspace_root: root,
-    build_target_dir: @fsutil.resolve_path(root, "build"),
     app_package: "app",
     config_path: @fsutil.resolve_path(root, "proton.project.json"),
     product_name: "Demo App",
@@ -35,8 +34,7 @@ fn macos_dmg_test_plan(root : String) -> PackagePlan {
 #cfg(not(platform="windows"))
 async test "macOS dmg uses drag-to-install layout and a verified UDZO image" {
   guard is_macos_host() else { return }
-  let root = @fsutil.resolve_path("target", "proton-package-dmg-real")
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-dmg-")
   let app = @fsutil.resolve_path(root, "Source.app")
   ensure_dir(@fsutil.resolve_path(app, "Contents"))
   write_text(
diff --git a/cli/package/package_wbtest.mbt b/cli/package/package_wbtest.mbt
index f8a8e8a5..146fc548 100644
--- a/cli/package/package_wbtest.mbt
+++ b/cli/package/package_wbtest.mbt
@@ -8,6 +8,14 @@ fn parse_package_matches(args : Array[String]) -> @argparse.Matches raise {
   command().parse(argv=args, env=Map([]))
 }
 
+///|
+fn restore_package_env(name : String, value : String?) -> Unit {
+  match value {
+    Some(value) => @env.set_env_var(name, value)
+    None => @env.unset_env_var(name)
+  }
+}
+
 ///|
 test "parse package args accepts repeated targets and overrides" {
   let raw = parse_package_args([
@@ -162,11 +170,6 @@ async test "package plan uses the host defaults" {
   assert_eq(plan.identifier, "dev.proton.demo")
   assert_eq(plan.version, "1.0.0")
   assert_false(plan.release)
-  assert_true(
-    normalize_slashes(plan.build_target_dir).has_suffix(
-      "/target/proton-package-build/dev-proton-demo",
-    ),
-  )
   let release_plan = build_package_plan(
     parse_package_args(["--release"]),
     "proton.project.json",
@@ -178,8 +181,7 @@ async test "package plan uses the host defaults" {
 
 ///|
 async test "package plan stages every window file entry" {
-  let root = @fsutil.resolve_path("target", "proton-package-window-entries")
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-window-entries-")
   let main = @fsutil.resolve_path(root, "pages/main.html")
   let secondary = @fsutil.resolve_path(root, "standalone/settings.html")
   ensure_dir(@fsutil.path_parent(main))
@@ -226,8 +228,7 @@ async test "package plan stages every window file entry" {
 
 ///|
 async test "configured signing binaries resolve through staged resources" {
-  let root = @fsutil.resolve_path("target", "proton-package-sign-binaries")
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-sign-binaries-")
   let binary = @fsutil.resolve_path(root, "bin/worker")
   ensure_dir(@fsutil.path_parent(binary))
   write_text(binary, "binary")
@@ -264,7 +265,7 @@ async test "configured signing binaries resolve through staged resources" {
 
 ///|
 async test "package plan uses configured backend module and package" {
-  let base_dir = @fsutil.resolve_path("target", "proton package module paths")
+  let base_dir = @async_fs.tmpdir(prefix="proton-package-module-paths-")
   let backend_path = @fsutil.resolve_path(base_dir, "modules/backend app")
   let project = @proton_config.ProjectConfig::new(
     base_dir,
@@ -300,7 +301,7 @@ async test "package plan uses configured backend module and package" {
 ///|
 #cfg(not(platform="windows"))
 test "macOS package paths normalize absolute and relative inputs" {
-  let base = @fsutil.resolve_path("target", "proton package path base")
+  let base = @fsutil.resolve_path("fixtures", "proton package path base")
   assert_eq(@fsutil.resolve_path(base, "/"), "/")
   assert_eq(
     @fsutil.resolve_path(base, "/tmp/proton absolute path"),
@@ -335,8 +336,7 @@ test "macOS package paths normalize absolute and relative inputs" {
 ///|
 #cfg(not(platform="windows"))
 async test "macOS ensure_dir recursively creates absolute paths with spaces" {
-  let root = @fsutil.resolve_path("target", "proton package ensure dir")
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-ensure-dir-")
   let nested = @fsutil.resolve_path(root, "parent with spaces/child/grandchild")
   ensure_dir(nested)
   assert_true(@fsutil.path_is_dir(nested))
@@ -502,9 +502,8 @@ test "macOS CEF process signing preserves hardened runtime and identifier" {
 
 ///|
 async test "macOS signing rejects a missing required target" {
-  let missing = @fsutil.resolve_path(
-    "target", "proton-package-missing-signing-target",
-  )
+  let root = @async_fs.tmpdir(prefix="proton-package-signing-target-")
+  let missing = @fsutil.resolve_path(root, "missing")
   remove_tree(missing)
   try
     require_macos_codesign_targets([
@@ -580,8 +579,7 @@ test "release project config preserves an already disabled or absent debug field
 
 ///|
 async test "macOS icon selection stages icns and rejects a missing source" {
-  let root = @fsutil.resolve_path("target", "proton-package-macos-icon")
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-macos-icon-")
   let resources = @fsutil.resolve_path(root, "Resources")
   let icon = @fsutil.resolve_path(root, "Demo.ICNS")
   ensure_dir(resources)
@@ -593,7 +591,6 @@ async test "macOS icon selection stages icns and rejects a missing source" {
   let plan = PackagePlan::{
     root,
     workspace_root: root,
-    build_target_dir: @fsutil.resolve_path(root, "build"),
     app_package: "app",
     config_path: @fsutil.resolve_path(root, "proton.project.json"),
     product_name: "Demo",
@@ -641,7 +638,6 @@ test "macOS plist contains bundle identity and executable" {
   let plan = PackagePlan::{
     root: ".",
     workspace_root: ".",
-    build_target_dir: "target/proton-package-build/dev-proton-demo",
     app_package: "app",
     config_path: "proton.project.json",
     product_name: "Demo & App",
@@ -651,7 +647,7 @@ test "macOS plist contains bundle identity and executable" {
     bundle_version: "1.2.3",
     update_revision: 42UL,
     targets: ["app"],
-    output: "target",
+    output: "dist",
     build: false,
     release: false,
     base_dir: ".",
@@ -690,12 +686,10 @@ test "macOS plist contains bundle identity and executable" {
 
 ///|
 async test "package manifest records launch metadata" {
-  let root = "target/proton-package-launch-metadata"
-  ensure_dir(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-launch-metadata-")
   let plan = PackagePlan::{
     root: ".",
     workspace_root: ".",
-    build_target_dir: "target/proton-package-build/dev-proton-demo",
     app_package: "app",
     config_path: "proton.project.json",
     product_name: "Demo",
@@ -705,7 +699,7 @@ async test "package manifest records launch metadata" {
     bundle_version: "1.2.3",
     update_revision: 0UL,
     targets: ["app"],
-    output: "target",
+    output: "dist",
     build: false,
     release: false,
     base_dir: ".",
@@ -759,7 +753,6 @@ test "macOS helper plist matches its bundle identity" {
   let plan = PackagePlan::{
     root: ".",
     workspace_root: ".",
-    build_target_dir: "target/proton-package-build/dev-proton-demo",
     app_package: "app",
     config_path: "proton.project.json",
     product_name: "Demo & App",
@@ -769,7 +762,7 @@ test "macOS helper plist matches its bundle identity" {
     bundle_version: "42",
     update_revision: 42UL,
     targets: ["app"],
-    output: "target",
+    output: "dist",
     build: false,
     release: false,
     base_dir: ".",
@@ -802,12 +795,10 @@ test "macOS helper plist matches its bundle identity" {
 ///|
 async test "macOS ZIP uses the final app name without metadata entries" {
   guard is_macos_host() else { return }
-  let root = @fsutil.resolve_path("target", "proton-package-macos-zip-layout")
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-macos-zip-")
   let plan = PackagePlan::{
     root,
     workspace_root: root,
-    build_target_dir: @fsutil.resolve_path(root, "build"),
     app_package: "app",
     config_path: @fsutil.resolve_path(root, "proton.project.json"),
     product_name: "Demo App",
@@ -861,8 +852,7 @@ async test "macOS ZIP uses the final app name without metadata entries" {
 
 ///|
 async test "macOS staged app promotion rolls back when staging is missing" {
-  let root = "target/proton-package-macos-promotion"
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-promotion-")
   let destination = @fsutil.resolve_path(root, "Demo.app")
   let marker = @fsutil.resolve_path(destination, "Contents/old.txt")
   ensure_dir(@fsutil.path_parent(marker))
@@ -885,8 +875,7 @@ async test "macOS staged app promotion rolls back when staging is missing" {
 
 ///|
 async test "macOS staged app promotion recovers an interrupted backup" {
-  let root = "target/proton-package-macos-stale-backup"
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-stale-backup-")
   let destination = @fsutil.resolve_path(root, "Demo.app")
   let backup = destination + ".backup"
   let marker = @fsutil.resolve_path(backup, "Contents/old.txt")
@@ -912,8 +901,7 @@ async test "macOS staged app promotion recovers an interrupted backup" {
 
 ///|
 async test "macOS artifact promotion rolls back the complete output set" {
-  let root = "target/proton-package-macos-transaction"
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-transaction-")
   let app = @fsutil.resolve_path(root, "Demo.app")
   let app_backup = app + ".backup"
   let staged_app = @fsutil.resolve_path(root, ".demo.staging.app")
@@ -955,8 +943,7 @@ async test "macOS artifact promotion rolls back the complete output set" {
 ///|
 async test "macOS notarization validates success and cleans failed upload" {
   guard is_macos_host() else { return }
-  let root = @fsutil.resolve_path("target", "proton-package-notarization-flow")
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-notarization-")
   let tools = @fsutil.resolve_path(root, "tools")
   let app = @fsutil.resolve_path(root, "Demo.app")
   let log = @fsutil.resolve_path(root, "commands.log")
@@ -979,7 +966,6 @@ async test "macOS notarization validates success and cleans failed upload" {
   let plan = PackagePlan::{
     root,
     workspace_root: root,
-    build_target_dir: @fsutil.resolve_path(root, "build"),
     app_package: "app",
     config_path: @fsutil.resolve_path(root, "proton.project.json"),
     product_name: "Demo",
@@ -1051,9 +1037,8 @@ async test "macOS notarization validates success and cleans failed upload" {
 
 ///|
 async test "package executable lookup ignores the dSYM mirror" {
-  let root = "target/proton-package-executable-lookup"
-  remove_tree(root)
-  let package_target = @fsutil.resolve_path(root, "package-target")
+  let root = @async_fs.tmpdir(prefix="proton-package-executable-")
+  let package_target = @fsutil.resolve_path(root, "workspace/_build")
   let unrelated = @fsutil.resolve_path(
     root, "workspace/native/release/build/other/app.exe",
   )
@@ -1062,7 +1047,6 @@ async test "package executable lookup ignores the dSYM mirror" {
   let plan = PackagePlan::{
     root,
     workspace_root: @fsutil.resolve_path(root, "workspace"),
-    build_target_dir: package_target,
     app_package: "app",
     config_path: @fsutil.resolve_path(root, "proton.project.json"),
     product_name: "Demo",
@@ -1107,8 +1091,7 @@ async test "package executable lookup ignores the dSYM mirror" {
 
 ///|
 async test "active runtime rejects another platform" {
-  let root = "target/proton-package-runtime-platform"
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-runtime-")
   ensure_dir(@fsutil.resolve_path(root, ".proton"))
   let old_dist = @env.get_env_var("PROTON_NATIVE_DIST")
   @env.unset_env_var("PROTON_NATIVE_DIST")
@@ -1136,7 +1119,7 @@ async test "active runtime rejects another platform" {
 
 ///|
 async test "Windows portable staging flattens runtime bin beside app executable" {
-  let root = "target/proton-package-windows-layout"
+  let root = @async_fs.tmpdir(prefix="proton-package-windows-")
   let output = @fsutil.resolve_path(root, "output")
   remove_tree(root)
   let runtime = prepare_windows_test_runtime(root)
@@ -1149,7 +1132,6 @@ async test "Windows portable staging flattens runtime bin beside app executable"
   let plan = PackagePlan::{
     root,
     workspace_root: root,
-    build_target_dir: @fsutil.resolve_path(root, "package-build"),
     app_package: "app",
     config_path: config,
     product_name: "Demo App",
diff --git a/cli/package/package_windows_wbtest.mbt b/cli/package/package_windows_wbtest.mbt
index 10bedb9e..b7821619 100644
--- a/cli/package/package_windows_wbtest.mbt
+++ b/cli/package/package_windows_wbtest.mbt
@@ -7,7 +7,6 @@ fn windows_test_plan(
   PackagePlan::{
     root,
     workspace_root: root,
-    build_target_dir: @fsutil.resolve_path(root, "package-build"),
     app_package: "app",
     config_path: @fsutil.resolve_path(root, "proton.project.json"),
     product_name: "Demo App",
@@ -154,7 +153,7 @@ test "Windows signtool args use SHA-256 and RFC3161 timestamp" {
 
 ///|
 test "Windows signing includes configured resource binaries" {
-  let root = "target/proton-package-windows-configured-signing"
+  let root = "fixtures/proton-package-windows-configured-signing"
   let plan = windows_test_plan(root, ["app"], true)
   plan.sign_binaries.push(@fsutil.resolve_path(root, "helpers/worker.exe"))
   let output = @fsutil.resolve_path(root, "portable")
@@ -168,8 +167,7 @@ test "Windows signing includes configured resource binaries" {
 ///|
 #cfg(platform="windows")
 async test "Windows signtool signs and verifies configured resource binaries" {
-  let root = "target/proton-package-windows-configured-signtool"
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-windows-signing-")
   let output = @fsutil.resolve_path(root, "portable")
   let plan = windows_test_plan(root, ["app"], true)
   let binary = @fsutil.resolve_path(root, "helpers/worker.exe")
@@ -210,8 +208,7 @@ async test "Windows signtool signs and verifies configured resource binaries" {
 
 ///|
 async test "Windows icon selection accepts ico and rejects a missing source" {
-  let root = "target/proton-package-windows-icon"
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-windows-icon-")
   let selected = @fsutil.resolve_path(root, "Demo.ICO")
   assert_eq(
     first_windows_icon(["icons/icon.png", selected, "icons/fallback.ico"]),
@@ -245,14 +242,16 @@ test "Windows icon embedding requires the native CLI backend" {
 ///|
 test "Windows path resolution keeps dotted relative children under the base" {
   let path = normalize_slashes(
-    @fsutil.resolve_path("target/proton-path-base", ".proton/runtime.json"),
+    @fsutil.resolve_path("fixtures/proton-path-base", ".proton/runtime.json"),
+  )
+  assert_true(
+    path.has_suffix("/fixtures/proton-path-base/.proton/runtime.json"),
   )
-  assert_true(path.has_suffix("/target/proton-path-base/.proton/runtime.json"))
 }
 
 ///|
 async test "Windows runtime validation rejects a missing required file" {
-  let root = "target/proton-package-windows-missing-runtime"
+  let root = @async_fs.tmpdir(prefix="proton-package-windows-runtime-")
   ignore(prepare_windows_test_inputs(root))
   let runtime = prepare_windows_test_runtime(root)
   let missing = @fsutil.resolve_path(runtime, "bin/chrome_elf.dll")
@@ -272,7 +271,7 @@ async test "Windows runtime validation rejects a missing required file" {
 
 ///|
 async test "Windows portable staging is atomic and excludes build artifacts" {
-  let root = "target/proton package windows layout with spaces"
+  let root = @async_fs.tmpdir(prefix="proton package windows layout ")
   let (executable, _) = prepare_windows_test_inputs(root)
   let runtime = prepare_windows_test_runtime(root)
   let plan = windows_test_plan(root, ["app"], false)
@@ -307,7 +306,7 @@ async test "Windows portable staging is atomic and excludes build artifacts" {
 
 ///|
 async test "Windows portable stages a configured signing binary from resources" {
-  let root = "target/proton-package-windows-resource-signing"
+  let root = @async_fs.tmpdir(prefix="proton-package-windows-resource-")
   let (executable, _) = prepare_windows_test_inputs(root)
   let binary = @fsutil.resolve_path(root, "helpers/worker.exe")
   write_windows_test_file(binary, "worker")
@@ -332,7 +331,7 @@ async test "Windows portable stages a configured signing binary from resources"
 ///|
 #cfg(platform="windows")
 async test "Windows portable zip is atomic and extracts from paths with spaces" {
-  let root = "target/proton-package-windows-zip with spaces"
+  let root = @async_fs.tmpdir(prefix="proton package windows zip ")
   let (executable, _) = prepare_windows_test_inputs(root)
   let runtime = prepare_windows_test_runtime(root)
   let plan = windows_test_plan(root, ["app", "zip"], false)
@@ -372,8 +371,7 @@ async test "Windows portable zip is atomic and extracts from paths with spaces"
 
 ///|
 async test "Windows promotion rolls back when staging is missing" {
-  let root = "target/proton-package-windows-rollback"
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-windows-rollback-")
   let destination = @fsutil.resolve_path(root, "Demo App")
   let marker = @fsutil.resolve_path(destination, "old.txt")
   write_windows_test_file(marker, "old")
@@ -396,8 +394,7 @@ async test "Windows promotion rolls back when staging is missing" {
 
 ///|
 async test "Windows promotion restores a stale backup before continuing" {
-  let root = "target/proton-package-windows-stale-backup"
-  remove_tree(root)
+  let root = @async_fs.tmpdir(prefix="proton-package-windows-backup-")
   let destination = @fsutil.resolve_path(root, "Demo App")
   let backup = destination + ".backup"
   let marker = @fsutil.resolve_path(backup, "old.txt")
@@ -421,7 +418,7 @@ async test "Windows promotion restores a stale backup before continuing" {
 
 ///|
 async test "Windows signing rejects a missing target before invoking signtool" {
-  let root = "target/proton-package-windows-missing-sign-target"
+  let root = @async_fs.tmpdir(prefix="proton-package-windows-sign-target-")
   let (_, _) = prepare_windows_test_inputs(root)
   let output = @fsutil.resolve_path(root, "portable")
   for
@@ -457,7 +454,7 @@ async test "Windows signing rejects a missing target before invoking signtool" {
 ///|
 #cfg(platform="windows")
 async test "Windows signing failure does not leak the certificate password" {
-  let root = "target/proton-package-windows-sign-failure"
+  let root = @async_fs.tmpdir(prefix="proton-package-windows-sign-failure-")
   let (_, _) = prepare_windows_test_inputs(root)
   let output = @fsutil.resolve_path(root, "portable")
   let plan = windows_test_plan(root, ["app"], true)
@@ -492,7 +489,7 @@ async test "Windows signing failure does not leak the certificate password" {
 ///|
 #cfg(platform="windows")
 async test "Windows signing failure blocks promotion" {
-  let root = "target/proton-package-windows-sign-promotion-failure"
+  let root = @async_fs.tmpdir(prefix="proton-package-windows-promotion-")
   let (executable, _) = prepare_windows_test_inputs(root)
   let runtime = prepare_windows_test_runtime(root)
   let plan = windows_test_plan(root, ["app"], true)
@@ -527,7 +524,7 @@ async test "Windows signing failure blocks promotion" {
 ///|
 #cfg(platform="windows")
 async test "Windows signature verification failure blocks promotion" {
-  let root = "target/proton-package-windows-verify-failure"
+  let root = @async_fs.tmpdir(prefix="proton-package-windows-verify-")
   let (executable, _) = prepare_windows_test_inputs(root)
   let runtime = prepare_windows_test_runtime(root)
   let plan = windows_test_plan(root, ["app"], true)
diff --git a/config/config_test.mbt b/config/config_test.mbt
index 56989070..8927ed57 100644
--- a/config/config_test.mbt
+++ b/config/config_test.mbt
@@ -14,14 +14,14 @@ test "project config reports malformed JSON at the text boundary" {
   let error = expect_project_config_error(() => {
     load_project_config_from_text(
       "{\"window\":",
-      "target/proton-config",
-      name="target/proton-config/proton.project.json",
+      "fixtures/proton-config",
+      name="fixtures/proton-config/proton.project.json",
     )
   })
   guard error is ProjectConfigError::Syntax(name~, diagnostics~) else {
     abort("expected project config JSON syntax error")
   }
-  assert_eq(name, "target/proton-config/proton.project.json")
+  assert_eq(name, "fixtures/proton-config/proton.project.json")
   assert_true(diagnostics != "")
   assert_true(error.message().has_prefix(name + ": "))
 }
@@ -38,7 +38,7 @@ test "project config rejects unsupported window size_hint" {
     "entry": { "kind": "url", "value": "http://localhost:5173" },
   }
   let error = expect_project_config_error(() => {
-    load_project_config_from_json(source, "target/proton-config")
+    load_project_config_from_json(source, "fixtures/proton-config")
   })
   assert_true(error.message().contains("unsupported window.size_hint"))
 }
@@ -54,7 +54,7 @@ test "project config parses default titlebar style" {
     },
     "entry": { "kind": "url", "value": "http://localhost:5173" },
   }
-  let config = load_project_config_from_json(source, "target/proton-config").config()
+  let config = load_project_config_from_json(source, "fixtures/proton-config").config()
   assert_true(config.window.titlebar_style == TitlebarDefault)
 }
 
@@ -69,7 +69,7 @@ test "project config parses overlay titlebar style" {
     },
     "entry": { "kind": "url", "value": "http://localhost:5173" },
   }
-  let config = load_project_config_from_json(source, "target/proton-config").config()
+  let config = load_project_config_from_json(source, "fixtures/proton-config").config()
   assert_true(config.window.titlebar_style == TitlebarOverlay)
 }
 
@@ -81,7 +81,7 @@ test "project config requires an identifier for single instance mode" {
     "entry": { "kind": "html", "value": "<main>App</main>" },
   }
   let error = expect_project_config_error(() => {
-    load_project_config_from_json(source, "target/proton-config")
+    load_project_config_from_json(source, "fixtures/proton-config")
   })
   assert_true(error.message().contains("identifier"))
   assert_true(error.message().contains("single_instance"))
@@ -95,7 +95,7 @@ test "project config decodes single instance mode" {
     "window": { "title": "App", "width": 900, "height": 700 },
     "entry": { "kind": "html", "value": "<main>App</main>" },
   }
-  let config = load_project_config_from_json(source, "target/proton-config").config()
+  let config = load_project_config_from_json(source, "fixtures/proton-config").config()
   assert_true(config.single_instance())
   assert_eq(config.metadata().identifier, Some("dev.proton.single-instance"))
 }
@@ -112,14 +112,14 @@ test "project config rejects unsupported titlebar style" {
     "entry": { "kind": "url", "value": "http://localhost:5173" },
   }
   let error = expect_project_config_error(() => {
-    load_project_config_from_json(source, "target/proton-config")
+    load_project_config_from_json(source, "fixtures/proton-config")
   })
   assert_true(error.message().contains("unsupported window.titlebar_style"))
 }
 
 ///|
 test "project config rebases file entry and frontend paths from config directory" {
-  let base_dir = "target/proton-config/subdir"
+  let base_dir = "fixtures/proton-config/subdir"
   let source : Json = {
     "window": { "title": "App", "width": 900, "height": 700 },
     "entry": { "kind": "asset", "value": "frontend/dist/index.html" },
@@ -134,7 +134,7 @@ test "project config rebases file entry and frontend paths from config directory
       "icon": ["icons/icon.ico"],
       "resources": ["resources/**"],
       "sign": { "binaries": ["bin/worker"] },
-      "output": "target/proton-dist",
+      "output": "custom-dist",
     },
   }
   let config = load_project_config_from_json(source, base_dir).config()
@@ -142,7 +142,7 @@ test "project config rebases file entry and frontend paths from config directory
     Asset(path) =>
       assert_true(
         normalize_test_path(path).has_suffix(
-          "target/proton-config/subdir/frontend/dist/index.html",
+          "fixtures/proton-config/subdir/frontend/dist/index.html",
         ),
       )
     _ => abort("expected asset entry")
@@ -151,41 +151,41 @@ test "project config rebases file entry and frontend paths from config directory
   assert_eq(backend.app_package(), "app")
   assert_true(
     normalize_test_path(backend.path()).has_suffix(
-      "target/proton-config/subdir/backend module",
+      "fixtures/proton-config/subdir/backend module",
     ),
   )
   let frontend = config.frontend().unwrap()
   assert_true(
     normalize_test_path(frontend.dist().unwrap()).has_suffix(
-      "target/proton-config/subdir/frontend module/dist",
+      "fixtures/proton-config/subdir/frontend module/dist",
     ),
   )
   assert_true(
     normalize_test_path(frontend.path().unwrap()).has_suffix(
-      "target/proton-config/subdir/frontend module",
+      "fixtures/proton-config/subdir/frontend module",
     ),
   )
   let bundle = config.bundle().unwrap()
   assert_eq(bundle.targets, ["app", "zip", "dmg"])
   assert_true(
     normalize_test_path(bundle.icon[0]).has_suffix(
-      "target/proton-config/subdir/icons/icon.ico",
+      "fixtures/proton-config/subdir/icons/icon.ico",
     ),
   )
   assert_true(
     normalize_test_path(bundle.resources[0]).has_suffix(
-      "target/proton-config/subdir/resources/**",
+      "fixtures/proton-config/subdir/resources/**",
     ),
   )
   let sign = bundle.sign.unwrap()
   assert_true(
     normalize_test_path(sign.binaries()[0]).has_suffix(
-      "target/proton-config/subdir/bin/worker",
+      "fixtures/proton-config/subdir/bin/worker",
     ),
   )
   assert_true(
     normalize_test_path(bundle.output()).has_suffix(
-      "target/proton-config/subdir/target/proton-dist",
+      "fixtures/proton-config/subdir/custom-dist",
     ),
   )
 }
@@ -279,14 +279,14 @@ test "project config rejects absolute project paths with field-specific errors"
       "bundle.output",
       project_config_for_path_test(
         html_entry,
-        extra=("bundle", { "output": "/target/proton-dist" }),
+        extra=("bundle", { "output": "/custom-dist" }),
       ),
     ),
   ]
   for _, item in cases {
     let (label, source) = item
     let error = expect_project_config_error(() => {
-      load_project_config_from_json(source, "target/proton-config")
+      load_project_config_from_json(source, "fixtures/proton-config")
     })
     assert_eq(
       error.message(),
@@ -304,7 +304,7 @@ test "project config rejects signing binary globs under the correct field" {
     extra=("bundle", { "sign": { "binaries": ["bin/*.exe"] } }),
   )
   let error = expect_project_config_error(() => {
-    load_project_config_from_json(source, "target/proton-config")
+    load_project_config_from_json(source, "fixtures/proton-config")
   })
   assert_eq(
     error.message(),
@@ -319,7 +319,7 @@ test "project config rejects backslashes in portable project paths" {
     "entry": { "kind": "asset", "value": "frontend\\dist\\index.html" },
   }
   let error = expect_project_config_error(() => {
-    load_project_config_from_json(source, "target/proton-config")
+    load_project_config_from_json(source, "fixtures/proton-config")
   })
   assert_eq(
     error.message(),
@@ -333,7 +333,7 @@ test "project config rebases portable paths into host path components" {
     "window": { "title": "App", "width": 900, "height": 700 },
     "entry": { "kind": "asset", "value": "frontend/dist/index.html" },
   }
-  let config = load_project_config_from_json(source, "target/proton-config").config()
+  let config = load_project_config_from_json(source, "fixtures/proton-config").config()
   match config.entry() {
     Asset(path) => {
       let entry : @mbpath.Path = path
@@ -346,37 +346,7 @@ test "project config rebases portable paths into host path components" {
 
 ///|
 test "project config reads module metadata from configured backend" {
-  let project_dir = "target/project-config-backend-metadata"
-  let backend_dir = project_dir + "/backend"
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.create_dir(project_dir) catch {
-    _ => ()
-  }
-  @mbfs.create_dir(backend_dir) catch {
-    _ => ()
-  }
-  @mbfs.write_string_to_file(
-    project_dir + "/moon.mod",
-    "name = \"example/parent\"\nversion = \"9.9.9\"\n",
-    encoding="utf8",
-  ) catch {
-    error => abort(@debug.render(Repr(error)))
-  }
-  @mbfs.write_string_to_file(
-    backend_dir + "/moon.mod",
-    (
-      #|name = "example/backend"
-      #|version = "1.2.3"
-      #|description = "Backend module metadata"
-      #|license = "Apache-2.0"
-      #|
-    ),
-    encoding="utf8",
-  ) catch {
-    error => abort(@debug.render(Repr(error)))
-  }
+  let project_dir = "testdata/project-config-backend-metadata"
   let source : Json = {
     "window": { "title": "App", "width": 900, "height": 700 },
     "entry": { "kind": "asset", "value": "frontend/dist/index.html" },
@@ -388,11 +358,13 @@ test "project config reads module metadata from configured backend" {
   assert_eq(metadata.version, Some("1.2.3"))
   assert_eq(metadata.description, Some("Backend module metadata"))
   assert_eq(metadata.license, Some("Apache-2.0"))
-  @mbfs.remove_file(backend_dir + "/moon.mod") catch {
-    error => abort(@debug.render(Repr(error)))
+  let source_without_backend_manifest : Json = {
+    "window": { "title": "App", "width": 900, "height": 700 },
+    "entry": { "kind": "asset", "value": "frontend/dist/index.html" },
+    "backend": { "path": "missing-backend", "package": "app" },
   }
   let metadata_without_backend_manifest = load_project_config_from_json(
-      source, project_dir,
+      source_without_backend_manifest, project_dir,
     )
     .config()
     .metadata()
@@ -407,7 +379,7 @@ test "project config rejects legacy frontend cwd" {
     "frontend": { "cwd": "frontend" },
   }
   let error = expect_project_config_error(() => {
-    load_project_config_from_json(source, "target/proton-config")
+    load_project_config_from_json(source, "fixtures/proton-config")
   })
   assert_eq(
     error.message(),
@@ -426,7 +398,7 @@ test "project config aggregates unknown top-level fields" {
     "debug": false,
   }
   let error = expect_project_config_error(() => {
-    load_project_config_from_json(source, "target/proton-config")
+    load_project_config_from_json(source, "fixtures/proton-config")
   })
   assert_eq(
     error.message(),
@@ -496,7 +468,7 @@ test "project config rejects unknown object fields" {
     "entry": { "kind": "url", "value": "http://localhost:5173" },
   }
   let error = expect_project_config_error(() => {
-    load_project_config_from_json(source, "target/proton-config")
+    load_project_config_from_json(source, "fixtures/proton-config")
   })
   assert_eq(
     error.message(),
@@ -510,7 +482,7 @@ test "project config load reports no warnings by default" {
     "window": { "title": "App", "width": 900, "height": 700 },
     "entry": { "kind": "url", "value": "http://localhost:5173" },
   }
-  let loaded = load_project_config_from_json(source, "target/proton-config")
+  let loaded = load_project_config_from_json(source, "fixtures/proton-config")
   assert_eq(loaded.warnings(), [])
 }
 
@@ -520,7 +492,7 @@ test "loaded project config carries warnings" {
     "window": { "title": "App", "width": 900, "height": 700 },
     "entry": { "kind": "url", "value": "http://localhost:5173" },
   }
-  let loaded = load_project_config_from_json(source, "target/proton-config")
+  let loaded = load_project_config_from_json(source, "fixtures/proton-config")
   let with_warnings = LoadedProjectConfig::new(loaded.config(), warnings=[
     "proton.project.json field `legacy` is deprecated",
   ])
@@ -555,7 +527,7 @@ test "project config decodes secondary windows and macOS launch metadata" {
       ],
     },
   }
-  let config = load_project_config_from_json(source, "target/proton-config").config()
+  let config = load_project_config_from_json(source, "fixtures/proton-config").config()
   assert_eq(config.windows().length(), 1)
   assert_eq(config.windows()[0].id, "settings")
   assert_true(config.windows()[0].open_on_start)
@@ -566,7 +538,7 @@ test "project config decodes secondary windows and macOS launch metadata" {
     ProjectEntry::File(path) =>
       assert_true(
         normalize_test_path(path).has_suffix(
-          "target/proton-config/settings.html",
+          "fixtures/proton-config/settings.html",
         ),
       )
     _ => abort("expected secondary file entry")
diff --git a/config/project_config.mbt b/config/project_config.mbt
index dbf1e05a..f22eac9b 100644
--- a/config/project_config.mbt
+++ b/config/project_config.mbt
@@ -238,7 +238,7 @@ pub fn ProjectBundleConfig::new(
   sign? : ProjectSignConfig? = None,
   url_schemes? : Array[String] = [],
   document_types? : Array[ProjectDocumentType] = [],
-  output? : String = "target/proton-dist",
+  output? : String = "dist",
 ) -> ProjectBundleConfig {
   ProjectBundleConfig::{
     active,
diff --git a/config/project_decode.mbt b/config/project_decode.mbt
index 2a32b96b..3fbe34a4 100644
--- a/config/project_decode.mbt
+++ b/config/project_decode.mbt
@@ -573,7 +573,7 @@ fn optional_project_bundle(
       let document_types = optional_project_document_types(bundle_fields)
       let output = rebase_project_path(
         optional_string_config_field(bundle_fields, "output", "bundle.output").unwrap_or(
-          "target/proton-dist",
+          "dist",
         ),
         base_dir,
         "bundle.output",
diff --git a/config/testdata/project-config-backend-metadata/backend/moon.mod b/config/testdata/project-config-backend-metadata/backend/moon.mod
new file mode 100644
index 00000000..0b88840d
--- /dev/null
+++ b/config/testdata/project-config-backend-metadata/backend/moon.mod
@@ -0,0 +1,4 @@
+name = "example/backend"
+version = "1.2.3"
+description = "Backend module metadata"
+license = "Apache-2.0"
diff --git a/config/testdata/project-config-backend-metadata/moon.mod b/config/testdata/project-config-backend-metadata/moon.mod
new file mode 100644
index 00000000..f090eff0
--- /dev/null
+++ b/config/testdata/project-config-backend-metadata/moon.mod
@@ -0,0 +1,2 @@
+name = "example/parent"
+version = "9.9.9"
diff --git a/e2e/test/app_commands_probe_wbtest.mbt b/e2e/test/app_commands_probe_wbtest.mbt
index a827a0b1..e71eef8d 100644
--- a/e2e/test/app_commands_probe_wbtest.mbt
+++ b/e2e/test/app_commands_probe_wbtest.mbt
@@ -75,7 +75,7 @@ async fn evaluate_json(
 
 ///|
 async fn run_app_commands_full_probe(
-  root : String,
+  output_root : String,
   target : String,
   timeout : Int,
   native_log_path : String,
@@ -94,7 +94,7 @@ async fn run_app_commands_full_probe(
   let queue = run_queue_full_probe(page)
   run_reload_probe(page, target, timeout)
   page_open = false
-  run_non_proton_probe(target, root, timeout)
+  run_non_proton_probe(target, output_root, timeout)
   assert_native_bridge_guards(native_log_path)
   println(
     "MoonBit 41_app_commands full probe passed: screenshot=" +
@@ -386,10 +386,10 @@ async fn run_reload_probe(
 ///|
 async fn run_non_proton_probe(
   target : String,
-  root : String,
+  output_root : String,
   timeout : Int,
 ) -> Unit {
-  let file_path = join_path(root, "target/non-proton-moonbit-probe.html")
+  let file_path = join_path(output_root, "non-proton-moonbit-probe.html")
   @mbfs.write_string_to_file(
     file_path, "<!doctype html><title>Non Proton File Probe</title><h1>file probe</h1>",
   ) catch {
diff --git a/e2e/test/dev_extension_process_wbtest.mbt b/e2e/test/dev_extension_process_wbtest.mbt
index 24193876..3a8c6df4 100644
--- a/e2e/test/dev_extension_process_wbtest.mbt
+++ b/e2e/test/dev_extension_process_wbtest.mbt
@@ -22,7 +22,11 @@ fn dev_extension_frontend_state(root : String) -> DevExtensionFrontendState {
 }
 
 ///|
-async fn ensure_dev_extension_frontend(root : String, timeout : Int) -> Unit {
+async fn ensure_dev_extension_frontend(
+  root : String,
+  output_root : String,
+  timeout : Int,
+) -> Unit {
   let frontend_dir = join_path(root, "examples/47_dev_extension_js/frontend")
   let vite = dev_extension_vite_binary(frontend_dir)
   if !@mbfs.path_exists(vite) {
@@ -30,7 +34,7 @@ async fn ensure_dev_extension_frontend(root : String, timeout : Int) -> Unit {
       "ci", "--no-audit", "--no-fund",
     ])
     run_dev_extension_command(
-      root,
+      output_root,
       "47-npm-ci",
       program,
       args,
@@ -99,30 +103,30 @@ fn process_snapshot_suffix(snapshot : ProcessSnapshot) -> String {
 
 ///|
 fn dev_extension_cli_target_dir(
-  root : String,
+  output_root : String,
   phase : String,
   port : Int,
 ) -> String {
-  join_path(root, "target/proton-e2e-cli-" + phase + "-" + port.to_string())
+  join_path(output_root, "cli-" + phase + "-" + port.to_string())
 }
 
 ///|
 fn dev_extension_app_target_dir(
-  root : String,
+  output_root : String,
   phase : String,
   port : Int,
 ) -> String {
-  join_path(root, "target/proton-e2e-app-" + phase + "-" + port.to_string())
+  join_path(output_root, "app-" + phase + "-" + port.to_string())
 }
 
 ///|
-fn dev_extension_example_target_dir(root : String, port : Int) -> String {
-  join_path(root, "target/proton-e2e-example-" + port.to_string())
+fn dev_extension_example_target_dir(output_root : String, port : Int) -> String {
+  join_path(output_root, "example-" + port.to_string())
 }
 
 ///|
 async fn run_dev_extension_command(
-  root : String,
+  output_root : String,
   name : String,
   program : String,
   args : Array[String],
@@ -130,10 +134,7 @@ async fn run_dev_extension_command(
   env : Map[String, String],
   timeout : Int,
 ) -> Unit {
-  @mbfs.create_dir(join_path(root, "target")) catch {
-    _ => ()
-  }
-  let output_path = join_path(root, "target/proton-e2e-" + name + ".log")
+  let output_path = join_path(output_root, name + ".log")
   @async.with_task_group(group => {
     let output = @process.redirect_to_file(
       output_path,
@@ -189,9 +190,10 @@ async fn run_dev_extension_command(
 ///|
 fn dev_extension_runtime_env(
   root : String,
+  output_root : String,
   cdp_port : Int,
 ) -> Map[String, String] raise {
-  let env = app_process_env(root, "47_dev_extension_js", cdp_port)
+  let env = app_process_env(root, output_root, "47_dev_extension_js", cdp_port)
   env["NO_COLOR"] = "1"
   env["FORCE_COLOR"] = "0"
   env["PROTON_NO_UPDATE_CHECK"] = "1"
@@ -215,9 +217,10 @@ fn restore_dev_extension_parent_preload(
 ///|
 fn dev_extension_host_env(
   root : String,
+  output_root : String,
   cdp_port : Int,
 ) -> Map[String, String] raise {
-  let env = dev_extension_runtime_env(root, cdp_port)
+  let env = dev_extension_runtime_env(root, output_root, cdp_port)
   // app_process_env injects libcef.so for Linux application children. The
   // CLI/build hosts launch Moon or Node rather than CEF, so restore the
   // caller's preload instead of leaking the injected CEF wrapper into them.
@@ -229,12 +232,13 @@ fn dev_extension_host_env(
 async fn spawn_dev_extension_cli_app(
   group : @async.TaskGroup[Unit],
   root : String,
+  output_root : String,
   cdp_port : Int,
   frontend_port : Int,
 ) -> SpawnedScenarioApp {
   let output_path = join_path(
-    root,
-    "target/proton-e2e-child-" + cdp_port.to_string() + ".log",
+    output_root,
+    "child-" + cdp_port.to_string() + ".log",
   )
   let output = @process.redirect_to_file(
     output_path,
@@ -248,7 +252,7 @@ async fn spawn_dev_extension_cli_app(
     "-C",
     join_path(root, "cli"),
     "--target-dir",
-    dev_extension_cli_target_dir(root, "dev", cdp_port),
+    dev_extension_cli_target_dir(output_root, "dev", cdp_port),
     "run",
     ".",
     "--",
@@ -260,7 +264,7 @@ async fn spawn_dev_extension_cli_app(
     "--package",
     ".",
     "--moon-target-dir",
-    dev_extension_app_target_dir(root, "dev", cdp_port),
+    dev_extension_app_target_dir(output_root, "dev", cdp_port),
     "--url",
     frontend_url,
     "--command",
@@ -276,7 +280,7 @@ async fn spawn_dev_extension_cli_app(
     program,
     args,
     cwd=root,
-    extra_env=dev_extension_host_env(root, cdp_port),
+    extra_env=dev_extension_host_env(root, output_root, cdp_port),
     stdout=output,
     stderr=output,
     cancel_handler=app_cancel_handler(),
@@ -285,7 +289,7 @@ async fn spawn_dev_extension_cli_app(
   SpawnedScenarioApp::{
     process,
     output_path,
-    native_log_path: scenario_native_log_path(root, cdp_port),
+    native_log_path: scenario_native_log_path(output_root, cdp_port),
   }
 }
 
@@ -293,11 +297,12 @@ async fn spawn_dev_extension_cli_app(
 async fn spawn_dev_extension_production_app(
   group : @async.TaskGroup[Unit],
   root : String,
+  output_root : String,
   cdp_port : Int,
 ) -> SpawnedScenarioApp {
   let output_path = join_path(
-    root,
-    "target/proton-e2e-child-" + cdp_port.to_string() + ".log",
+    output_root,
+    "child-" + cdp_port.to_string() + ".log",
   )
   let output = @process.redirect_to_file(
     output_path,
@@ -307,7 +312,7 @@ async fn spawn_dev_extension_production_app(
     "-C",
     join_path(root, "examples"),
     "--target-dir",
-    dev_extension_example_target_dir(root, cdp_port),
+    dev_extension_example_target_dir(output_root, cdp_port),
     "run",
     "47_dev_extension_js",
     "--target",
@@ -320,7 +325,7 @@ async fn spawn_dev_extension_production_app(
     program,
     args,
     cwd=root,
-    extra_env=dev_extension_runtime_env(root, cdp_port),
+    extra_env=dev_extension_runtime_env(root, output_root, cdp_port),
     stdout=output,
     stderr=output,
     cancel_handler=app_cancel_handler(),
@@ -329,27 +334,31 @@ async fn spawn_dev_extension_production_app(
   SpawnedScenarioApp::{
     process,
     output_path,
-    native_log_path: scenario_native_log_path(root, cdp_port),
+    native_log_path: scenario_native_log_path(output_root, cdp_port),
   }
 }
 
 ///|
-async fn build_dev_extension_frontend(root : String, timeout : Int) -> Unit {
+async fn build_dev_extension_frontend(
+  root : String,
+  output_root : String,
+  timeout : Int,
+) -> Unit {
   let runtime_dist = active_runtime_dist(root)
   let has_linux_cef = @mbfs.path_exists(
     join_path(runtime_dist, "bin/libcef.so"),
   )
   let timeout = dev_extension_build_timeout(timeout, has_linux_cef)
   let port = choose_cdp_port()
-  let env = dev_extension_host_env(root, port)
-  let cli_target_dir = dev_extension_cli_target_dir(root, "build", port)
-  let app_target_dir = dev_extension_app_target_dir(root, "build", port)
+  let env = dev_extension_host_env(root, output_root, port)
+  let cli_target_dir = dev_extension_cli_target_dir(output_root, "build", port)
+  let app_target_dir = dev_extension_app_target_dir(output_root, "build", port)
   defer {
     remove_dev_extension_tree(cli_target_dir)
     remove_dev_extension_tree(app_target_dir)
   }
   run_dev_extension_command(
-    root,
+    output_root,
     "47-proton-build",
     "moon",
     [
@@ -379,16 +388,23 @@ async fn build_dev_extension_frontend(root : String, timeout : Int) -> Unit {
 ///|
 async fn run_dev_extension_dev_probe_once(
   root : String,
+  output_root : String,
   frontend_port : Int,
   timeout : Int,
 ) -> Unit {
   let cdp_port = choose_cdp_port()
   let target = cdp_port.to_string()
   let frontend_url = "http://127.0.0.1:" + frontend_port.to_string()
-  let cli_target_dir = dev_extension_cli_target_dir(root, "dev", cdp_port)
-  let app_target_dir = dev_extension_app_target_dir(root, "dev", cdp_port)
+  let cli_target_dir = dev_extension_cli_target_dir(
+    output_root, "dev", cdp_port,
+  )
+  let app_target_dir = dev_extension_app_target_dir(
+    output_root, "dev", cdp_port,
+  )
   @async.with_task_group(group => {
-    let app = spawn_dev_extension_cli_app(group, root, cdp_port, frontend_port)
+    let app = spawn_dev_extension_cli_app(
+      group, root, output_root, cdp_port, frontend_port,
+    )
     let mut stopped = false
     defer {
       if !stopped {
@@ -400,7 +416,9 @@ async fn run_dev_extension_dev_probe_once(
     ignore(
       wait_for_spawned_app_cdp(app, cdp_http_endpoint_from(target), timeout),
     )
-    run_dev_extension_page_probe(app, target, frontend_url, root, timeout)
+    run_dev_extension_page_probe(
+      app, target, frontend_url, output_root, timeout,
+    )
     match app_exit_code(app.process) {
       Some(code) =>
         fail(
@@ -422,13 +440,18 @@ async fn run_dev_extension_dev_probe_once(
 ///|
 async fn run_dev_extension_production_probe_once(
   root : String,
+  output_root : String,
   timeout : Int,
 ) -> Unit {
   let cdp_port = choose_cdp_port()
   let target = cdp_port.to_string()
-  let example_target_dir = dev_extension_example_target_dir(root, cdp_port)
+  let example_target_dir = dev_extension_example_target_dir(
+    output_root, cdp_port,
+  )
   @async.with_task_group(group => {
-    let app = spawn_dev_extension_production_app(group, root, cdp_port)
+    let app = spawn_dev_extension_production_app(
+      group, root, output_root, cdp_port,
+    )
     let mut stopped = false
     defer {
       if !stopped {
@@ -459,7 +482,11 @@ async fn run_dev_extension_production_probe_once(
 }
 
 ///|
-async fn run_dev_extension_scenario_once(root : String, timeout : Int) -> Unit {
+async fn run_dev_extension_scenario_once(
+  root : String,
+  output_root : String,
+  timeout : Int,
+) -> Unit {
   let frontend = dev_extension_frontend_state(root)
   defer {
     if !frontend.had_node_modules {
@@ -469,18 +496,22 @@ async fn run_dev_extension_scenario_once(root : String, timeout : Int) -> Unit {
       remove_dev_extension_tree(frontend.dist_dir)
     }
   }
-  ensure_dev_extension_frontend(root, timeout)
+  ensure_dev_extension_frontend(root, output_root, timeout)
   let frontend_port = choose_cdp_port()
   run_e2e_operation_with_timeout(
     timeout,
     "47_dev_extension_js development probe",
-    () => run_dev_extension_dev_probe_once(root, frontend_port, timeout),
+    () => {
+      run_dev_extension_dev_probe_once(
+        root, output_root, frontend_port, timeout,
+      )
+    },
   )
-  build_dev_extension_frontend(root, timeout)
+  build_dev_extension_frontend(root, output_root, timeout)
   run_e2e_operation_with_timeout(
     timeout,
     "47_dev_extension_js production probe",
-    () => run_dev_extension_production_probe_once(root, timeout),
+    () => run_dev_extension_production_probe_once(root, output_root, timeout),
   )
 }
 
@@ -489,10 +520,12 @@ async fn run_dev_extension_scenario_with_retry(
   root : String,
   timeout : Int,
 ) -> Unit {
+  let output_root = @fs.tmpdir(prefix="proton-e2e-dev-extension-")
+  defer remove_dev_extension_tree(output_root)
   let mut attempt = 0
   while attempt < 2 {
     let succeeded = try {
-      run_dev_extension_scenario_once(root, timeout)
+      run_dev_extension_scenario_once(root, output_root, timeout)
       true
     } catch {
       error => {
diff --git a/e2e/test/dev_extension_scenario_wbtest.mbt b/e2e/test/dev_extension_scenario_wbtest.mbt
index 81f95a57..c59d22df 100644
--- a/e2e/test/dev_extension_scenario_wbtest.mbt
+++ b/e2e/test/dev_extension_scenario_wbtest.mbt
@@ -58,7 +58,7 @@ async fn run_dev_extension_page_probe(
   app : SpawnedScenarioApp,
   target : String,
   frontend_url : String,
-  root : String,
+  output_root : String,
   timeout : Int,
 ) -> Unit {
   let page = connect_spawned_page(app, target, timeout)
@@ -71,7 +71,7 @@ async fn run_dev_extension_page_probe(
   assert_dev_extension_probe(result, frontend_url, value)
   run_dev_extension_reload_probe(page, target, frontend_url, timeout)
   page_open = false
-  run_dev_extension_non_proton_probe(target, root, timeout)
+  run_dev_extension_non_proton_probe(target, output_root, timeout)
   assert_dev_extension_native_log(app.native_log_path)
   println("MoonBit 47_dev_extension_js dev probe passed")
 }
@@ -337,10 +337,10 @@ fn dev_extension_reload_probe_expression() -> String {
 ///|
 async fn run_dev_extension_non_proton_probe(
   target : String,
-  root : String,
+  output_root : String,
   timeout : Int,
 ) -> Unit {
-  let file_path = join_path(root, "target/non-proton-dev-extension-probe.html")
+  let file_path = join_path(output_root, "non-proton-dev-extension-probe.html")
   @mbfs.write_string_to_file(
     file_path, "<!doctype html><title>Non Proton File Probe</title><h1>file probe</h1>",
   ) catch {
diff --git a/e2e/test/orchestration_wbtest.mbt b/e2e/test/orchestration_wbtest.mbt
index 9bd22845..ff08c9b7 100644
--- a/e2e/test/orchestration_wbtest.mbt
+++ b/e2e/test/orchestration_wbtest.mbt
@@ -115,6 +115,7 @@ fn read_runtime_dist(manifest_path : String) -> Result[String, String] {
 ///|
 fn app_process_env(
   root : String,
+  output_root : String,
   scenario : String,
   cdp_port : Int,
 ) -> Map[String, String] raise {
@@ -138,7 +139,7 @@ fn app_process_env(
     "PROTON_NATIVE_DIST": runtime_dist,
     "PROTON_RUNTIME_ROOT": runtime_dist,
     "PROTON_HELPER_PATH": helper_path,
-    "PROTON_NATIVE_LOG": scenario_native_log_path(root, cdp_port),
+    "PROTON_NATIVE_LOG": scenario_native_log_path(output_root, cdp_port),
     "PROTON_REMOTE_DEBUGGING_PORT": cdp_port.to_string(),
     "PROTON_HEADLESS": "1",
     "PROTON_E2E_ASSET_SIDECAR_ENTRY": join_path(
@@ -191,8 +192,8 @@ fn helper_executable_name() -> String {
 }
 
 ///|
-fn scenario_native_log_path(root : String, cdp_port : Int) -> String {
-  join_path(root, "target/proton-e2e-" + cdp_port.to_string() + ".log")
+fn scenario_native_log_path(output_root : String, cdp_port : Int) -> String {
+  join_path(output_root, "native-" + cdp_port.to_string() + ".log")
 }
 
 ///|
@@ -229,17 +230,14 @@ fn path_list_separator() -> String {
 async fn[X] spawn_scenario_app(
   group : @async.TaskGroup[X],
   root : String,
+  output_root : String,
   scenario : String,
   cdp_port : Int,
 ) -> SpawnedScenarioApp {
-  let (program, args) = scenario_app_command(root)
-  let output_dir = join_path(root, "target")
-  if !@mbfs.path_exists(output_dir) {
-    @mbfs.create_dir(output_dir)
-  }
+  let (program, args) = scenario_app_command(output_root)
   let output_path = join_path(
-    root,
-    "target/proton-e2e-child-" + cdp_port.to_string() + ".log",
+    output_root,
+    "child-" + cdp_port.to_string() + ".log",
   )
   let output = @process.redirect_to_file(
     output_path,
@@ -250,7 +248,7 @@ async fn[X] spawn_scenario_app(
     program,
     args,
     cwd=root,
-    extra_env=app_process_env(root, scenario, cdp_port),
+    extra_env=app_process_env(root, output_root, scenario, cdp_port),
     stdout=output,
     stderr=output,
     cancel_handler=app_cancel_handler(),
@@ -259,18 +257,21 @@ async fn[X] spawn_scenario_app(
   SpawnedScenarioApp::{
     process,
     output_path,
-    native_log_path: scenario_native_log_path(root, cdp_port),
+    native_log_path: scenario_native_log_path(output_root, cdp_port),
   }
 }
 
 ///|
-async fn build_scenario_app_executable(root : String) -> Unit {
+async fn build_scenario_app_executable(
+  root : String,
+  output_root : String,
+) -> Unit {
   if @path.sep != '\\' {
     let (code, _) = @process.collect_output_merged(
       "moon",
       [
         "--target-dir",
-        scenario_app_target_dir(root),
+        scenario_app_target_dir(output_root),
         "-C",
         root,
         "test",
@@ -290,25 +291,25 @@ async fn build_scenario_app_executable(root : String) -> Unit {
 }
 
 ///|
-fn scenario_app_command(root : String) -> (String, Array[String]) raise {
+fn scenario_app_command(output_root : String) -> (String, Array[String]) raise {
   if @path.sep == '\\' {
     (current_test_executable(), [app_child_test_selector])
   } else {
-    isolated_app_command(scenario_app_executable(root), [
+    isolated_app_command(scenario_app_executable(output_root), [
       app_child_test_selector,
     ])
   }
 }
 
 ///|
-fn scenario_app_target_dir(root : String) -> String {
-  join_path(root, "target/proton-e2e-app-child")
+fn scenario_app_target_dir(output_root : String) -> String {
+  join_path(output_root, "app-build")
 }
 
 ///|
-fn scenario_app_executable(root : String) -> String {
+fn scenario_app_executable(output_root : String) -> String {
   join_path(
-    scenario_app_target_dir(root),
+    scenario_app_target_dir(output_root),
     "native/debug/test/moonbit-community/proton/e2e/test/test.whitebox_test.exe",
   )
 }
@@ -617,13 +618,14 @@ fn join_path(base : String, child : String) -> String {
 ///|
 async fn run_scenario_probe_once(
   root : String,
+  output_root : String,
   name : String,
   timeout : Int,
 ) -> Unit {
   let port = choose_cdp_port()
   let target = port.to_string()
   @async.with_task_group(group => {
-    let app = spawn_scenario_app(group, root, name, port)
+    let app = spawn_scenario_app(group, root, output_root, name, port)
     let mut stopped = false
     defer (if !stopped { app.process.cancel() })
     let browser_web_socket_url = wait_for_spawned_app_cdp(
@@ -651,7 +653,12 @@ async fn run_scenario_probe_once(
       finish_scenario_app(app, target)
     } else {
       if name == "41_app_commands" {
-        run_app_commands_full_probe(root, target, timeout, app.native_log_path)
+        run_app_commands_full_probe(
+          output_root,
+          target,
+          timeout,
+          app.native_log_path,
+        )
       } else if name == "40_event_broadcast" {
         run_event_scenario_page_probe(app, target, timeout)
       } else if name == "46_asset_sidecar_resources" {
@@ -692,7 +699,9 @@ async fn run_scenario_probe_with_retry(
   name : String,
   timeout : Int,
 ) -> Unit {
-  build_scenario_app_executable(root)
+  let output_root = @fs.tmpdir(prefix="proton-e2e-")
+  defer remove_dev_extension_tree(output_root)
+  build_scenario_app_executable(root, output_root)
   let operation_timeout = scenario_operation_timeout(name, timeout)
   let mut attempt = 0
   while attempt < 2 {
@@ -700,7 +709,7 @@ async fn run_scenario_probe_with_retry(
       run_e2e_operation_with_timeout(
         operation_timeout,
         "E2E scenario " + name,
-        () => run_scenario_probe_once(root, name, timeout),
+        () => run_scenario_probe_once(root, output_root, name, timeout),
       )
       true
     } catch {
diff --git a/e2e/test/process_lifecycle_wbtest.mbt b/e2e/test/process_lifecycle_wbtest.mbt
index ab55b8ee..0db402ca 100644
--- a/e2e/test/process_lifecycle_wbtest.mbt
+++ b/e2e/test/process_lifecycle_wbtest.mbt
@@ -328,12 +328,16 @@ async fn wait_for_cdp_endpoint_stop(endpoint : String, timeout : Int) -> Unit {
 }
 
 ///|
-async fn run_pending_lifecycle_probe_once(root : String, timeout : Int) -> Unit {
+async fn run_pending_lifecycle_probe_once(
+  root : String,
+  output_root : String,
+  timeout : Int,
+) -> Unit {
   let name = "41_app_commands"
   let port = choose_cdp_port()
   let target = port.to_string()
   @async.with_task_group(group => {
-    let app = spawn_scenario_app(group, root, name, port)
+    let app = spawn_scenario_app(group, root, output_root, name, port)
     let mut stopped = false
     defer (if !stopped { app.process.cancel() })
     ignore(
@@ -397,13 +401,16 @@ async fn run_pending_lifecycle_probe_once(root : String, timeout : Int) -> Unit
 
 ///|
 async fn run_pending_lifecycle_probe(root : String, timeout : Int) -> Unit {
+  let output_root = @fs.tmpdir(prefix="proton-e2e-lifecycle-")
+  defer remove_dev_extension_tree(output_root)
+  build_scenario_app_executable(root, output_root)
   let mut attempt = 0
   while attempt < 2 {
     let succeeded = try {
       run_e2e_operation_with_timeout(
         timeout,
         "41_app_commands pending lifecycle",
-        () => run_pending_lifecycle_probe_once(root, timeout),
+        () => run_pending_lifecycle_probe_once(root, output_root, timeout),
       )
       true
     } catch {
@@ -424,12 +431,16 @@ async fn run_pending_lifecycle_probe(root : String, timeout : Int) -> Unit {
 }
 
 ///|
-async fn run_event_lifecycle_probe_once(root : String, timeout : Int) -> Unit {
+async fn run_event_lifecycle_probe_once(
+  root : String,
+  output_root : String,
+  timeout : Int,
+) -> Unit {
   let name = "40_event_broadcast"
   let port = choose_cdp_port()
   let target = port.to_string()
   @async.with_task_group(group => {
-    let app = spawn_scenario_app(group, root, name, port)
+    let app = spawn_scenario_app(group, root, output_root, name, port)
     let mut stopped = false
     defer (if !stopped { app.process.cancel() })
     ignore(
@@ -491,13 +502,16 @@ async fn run_event_lifecycle_probe_once(root : String, timeout : Int) -> Unit {
 
 ///|
 async fn run_event_lifecycle_probe(root : String, timeout : Int) -> Unit {
+  let output_root = @fs.tmpdir(prefix="proton-e2e-lifecycle-")
+  defer remove_dev_extension_tree(output_root)
+  build_scenario_app_executable(root, output_root)
   let mut attempt = 0
   while attempt < 2 {
     let succeeded = try {
       run_e2e_operation_with_timeout(
         timeout,
         "40_event_broadcast event lifecycle",
-        () => run_event_lifecycle_probe_once(root, timeout),
+        () => run_event_lifecycle_probe_once(root, output_root, timeout),
       )
       true
     } catch {
diff --git a/e2e/test/scenario_validation_wbtest.mbt b/e2e/test/scenario_validation_wbtest.mbt
index 8defad43..0902cff4 100644
--- a/e2e/test/scenario_validation_wbtest.mbt
+++ b/e2e/test/scenario_validation_wbtest.mbt
@@ -105,14 +105,9 @@ test "Unix E2E cancellation targets the isolated process group first" {
 #cfg(not(platform="windows"))
 async test "Unix E2E cancellation terminates a real child process tree" {
   let root = repository_root()
-  let pid_path = join_path(
-    root,
-    "target/proton-e2e-cancel-child-" + choose_cdp_port().to_string() + ".pid",
-  )
-  @mbfs.remove_file(pid_path) catch {
-    _ => ()
-  }
-  defer (@mbfs.remove_file(pid_path) catch { _ => () })
+  let output_root = @fs.tmpdir(prefix="proton-e2e-cancel-")
+  defer remove_dev_extension_tree(output_root)
+  let pid_path = join_path(output_root, "child.pid")
   @async.with_task_group(group => {
     let (program, args) = isolated_app_command("/bin/sh", [
       "-c", "sleep 30 & child=$!; printf '%s' \"$child\" > \"$1\"; while :; do sleep 30; done",
diff --git a/examples/44_project_config/main.mbt b/examples/44_project_config/main.mbt
index bc97114e..ff3d654c 100644
--- a/examples/44_project_config/main.mbt
+++ b/examples/44_project_config/main.mbt
@@ -85,11 +85,7 @@ fn main {
   let bundle = require_some(config.bundle(), "bundle")
   assert_bool(bundle.active(), true, "bundle.active")
   assert_strings(bundle.targets(), ["app", "zip"], "bundle.targets")
-  assert_path_suffix(
-    bundle.output(),
-    "44_project_config/target/proton-dist",
-    "bundle.output",
-  )
+  assert_path_suffix(bundle.output(), "44_project_config/dist", "bundle.output")
 
   match config.dev_manifest().manifest().entry {
     @manifest.AppEntry::Url(url) =>
diff --git a/examples/44_project_config/proton.project.json b/examples/44_project_config/proton.project.json
index 1c575419..5ebfa90f 100644
--- a/examples/44_project_config/proton.project.json
+++ b/examples/44_project_config/proton.project.json
@@ -32,6 +32,6 @@
     "resources": [
       "resources/**"
     ],
-    "output": "target/proton-dist"
+    "output": "dist"
   }
 }
diff --git a/examples/46_asset_sidecar_resources/commands.mbt b/examples/46_asset_sidecar_resources/commands.mbt
index e184c810..98f2147b 100644
--- a/examples/46_asset_sidecar_resources/commands.mbt
+++ b/examples/46_asset_sidecar_resources/commands.mbt
@@ -41,12 +41,6 @@ async fn add_later(request : AddRequest) -> Int {
 #proton.command(contract=report_probe_command)
 fn report_probe(request : ReportProbeRequest) -> Unit {
   println("[asset-sidecar] " + request.report)
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.write_string_to_file("target/asset-sidecar.probe.json", request.report) catch {
-    _ => ()
-  }
 }
 
 ///|
diff --git a/examples/46_asset_sidecar_resources/moon.pkg b/examples/46_asset_sidecar_resources/moon.pkg
index 123f6d0d..1b9cd07f 100644
--- a/examples/46_asset_sidecar_resources/moon.pkg
+++ b/examples/46_asset_sidecar_resources/moon.pkg
@@ -1,5 +1,4 @@
 import {
-  "moonbitlang/x/fs" @mbfs,
   "moonbitlang/core/json",
   "moonbitlang/async",
   "moonbit-community/proton/extension" @proton_extension,
diff --git a/examples/47_dev_extension_js/proton.project.json b/examples/47_dev_extension_js/proton.project.json
index b4e61182..d71a5be5 100644
--- a/examples/47_dev_extension_js/proton.project.json
+++ b/examples/47_dev_extension_js/proton.project.json
@@ -12,6 +12,10 @@
     "value": "frontend/dist/index.html"
   },
   "debug": true,
+  "backend": {
+    "path": "..",
+    "package": "47_dev_extension_js"
+  },
   "frontend": {
     "dev_url": "http://127.0.0.1:5173",
     "path": "frontend",
@@ -25,6 +29,6 @@
       "app",
       "zip"
     ],
-    "output": "target/proton-dist"
+    "output": "dist"
   }
 }
diff --git a/examples/app_commands_fixture/app_commands.mbt b/examples/app_commands_fixture/app_commands.mbt
index 3bed9ad7..a75c4e74 100644
--- a/examples/app_commands_fixture/app_commands.mbt
+++ b/examples/app_commands_fixture/app_commands.mbt
@@ -99,12 +99,6 @@ fn fail(payload : FailPayload) -> String raise AppCommandError {
 ///|
 fn report_probe(payload : ReportProbePayload) -> ReportProbeReply {
   println("[app-commands] " + payload.report)
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.write_string_to_file("target/app-commands.probe.json", payload.report) catch {
-    _ => ()
-  }
   ReportProbeReply::{ ok: true }
 }
 
diff --git a/examples/app_commands_fixture/moon.pkg b/examples/app_commands_fixture/moon.pkg
index bb58ee10..07c3b3d9 100644
--- a/examples/app_commands_fixture/moon.pkg
+++ b/examples/app_commands_fixture/moon.pkg
@@ -1,5 +1,4 @@
 import {
-  "moonbitlang/x/fs" @mbfs,
   "moonbitlang/core/json",
   "moonbitlang/async",
   "moonbit-community/proton/extension" @proton_extension,
diff --git a/examples/e2e_fixtures/asset_sidecar.mbt b/examples/e2e_fixtures/asset_sidecar.mbt
index c4b8b7ee..662d6442 100644
--- a/examples/e2e_fixtures/asset_sidecar.mbt
+++ b/examples/e2e_fixtures/asset_sidecar.mbt
@@ -52,15 +52,6 @@ fn asset_sidecar_extension() -> @proton_extension.Extension {
       })
       registrar.bind(asset_sidecar_report_command, (_context, payload) => {
         println("[asset-sidecar-e2e] " + payload.report)
-        @mbfs.create_dir("target") catch {
-          _ => ()
-        }
-        @mbfs.write_string_to_file(
-          "target/asset-sidecar-e2e.probe.json",
-          payload.report,
-        ) catch {
-          _ => ()
-        }
       })
     },
   )
diff --git a/examples/e2e_fixtures/web_contents_view.mbt b/examples/e2e_fixtures/web_contents_view.mbt
index e63e3971..6e565646 100644
--- a/examples/e2e_fixtures/web_contents_view.mbt
+++ b/examples/e2e_fixtures/web_contents_view.mbt
@@ -228,12 +228,15 @@ async fn run_web_contents_view_pump(
       ignore(wakeup.wait())
     }
   }
-  let events_path = match @env.get_env_var("PROTON_NATIVE_LOG") {
-    Some(native_log) => native_log + ".view-events"
-    None => "target/proton-e2e-view-events.json"
-  }
-  @mbfs.write_string_to_file(events_path, view_events.join("\n")) catch {
-    _ => ()
+  match @env.get_env_var("PROTON_NATIVE_LOG") {
+    Some(native_log) =>
+      @mbfs.write_string_to_file(
+        native_log + ".view-events",
+        view_events.join("\n"),
+      ) catch {
+        _ => ()
+      }
+    None => ()
   }
   Ok(())
 }
diff --git a/examples/moon.mod b/examples/moon.mod
index 13614c00..1e1f7aa0 100644
--- a/examples/moon.mod
+++ b/examples/moon.mod
@@ -24,12 +24,12 @@ rule(name: "embed", command: ":embed -i $input -o $output")
 
 rule(
   name: "proton_codegen",
-  command: "moon -C \"$mod_dir/../codegen\" run --target-dir \"$mod_dir/target/proton-codegen-moon\" --target wasm . -- -C \"$mod_dir\" \"$input\" -o \"$output\"",
+  command: "moon -C \"$mod_dir/../codegen\" run --target-dir \"$mod_dir/../codegen/_build\" --target wasm . -- -C \"$mod_dir\" \"$input\" -o \"$output\"",
 )
 
 rule(
   name: "proton_extension_identity_codegen",
-  command: "moon -C \"$mod_dir/../codegen\" run --target-dir \"$mod_dir/target/proton-codegen-moon\" --target wasm . -- -C \"$mod_dir\" --extension-identity \"$input\" -o \"$output\"",
+  command: "moon -C \"$mod_dir/../codegen\" run --target-dir \"$mod_dir/../codegen/_build\" --target wasm . -- -C \"$mod_dir\" --extension-identity \"$input\" -o \"$output\"",
 )
 
 source = ""
diff --git a/native/scripts/verify_link_config.mjs b/native/scripts/verify_link_config.mjs
index 1b50ab74..4ed30bd5 100644
--- a/native/scripts/verify_link_config.mjs
+++ b/native/scripts/verify_link_config.mjs
@@ -106,23 +106,6 @@ if (!linkFlags.includes(expectedLinkNeedle)) {
   );
 }
 
-if (process.platform === "darwin") {
-  const packageRpath = "@executable_path/../Resources/proton/lib";
-  const packageConfig = readLinkConfig({
-    env: {
-      PROTON_NATIVE_DIST: dist,
-      PROTON_PACKAGE_RPATH: packageRpath,
-    },
-  });
-  const packageFlags = packageConfig?.vars?.PROTON_NATIVE_LINK_FLAGS ?? "";
-  if (!packageFlags.includes(packageRpath)) {
-    fail(`package rpath is missing from native link flags: ${packageFlags}`);
-  }
-  if (packageFlags.includes(`-rpath,\"${normalizedForLink(libDir)}\"`)) {
-    fail(`package link flags retain the absolute runtime rpath: ${packageFlags}`);
-  }
-}
-
 if (fs.existsSync(developmentDist)) {
   const isolatedCwd = fs.mkdtempSync(
     path.join(os.tmpdir(), "proton-link-config-"),
diff --git a/proton/bootstrap/config_paths_wbtest.mbt b/proton/bootstrap/config_paths_wbtest.mbt
index 089faa9c..bb655e9a 100644
--- a/proton/bootstrap/config_paths_wbtest.mbt
+++ b/proton/bootstrap/config_paths_wbtest.mbt
@@ -3,7 +3,7 @@ test "runtime config rebases portable paths into host path components" {
   let entry = build_app_entry_from_parts(
     "asset",
     "frontend/dist/index.html",
-    Some("target/proton-runtime-config"),
+    Some("fixtures/proton-runtime-config"),
   )
   match entry {
     Asset(path) => {
diff --git a/proton/bootstrap/config_test.mbt b/proton/bootstrap/config_test.mbt
index 289600f5..f0d35f4b 100644
--- a/proton/bootstrap/config_test.mbt
+++ b/proton/bootstrap/config_test.mbt
@@ -51,17 +51,12 @@ fn[T] expect_bootstrap_error(
 ///|
 /// Writes a minimal proton.project.json with one extra top-level field and checks the error.
 fn expect_project_extra_field_error(
+  root : String,
   key : String,
   value : Json,
   expected : String,
 ) -> Unit {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.create_dir("target/proton-extra-field") catch {
-    _ => ()
-  }
-  let config_path = "target/proton-extra-field/proton.project.json"
+  let config_path = root + "/proton.project.json"
   let config : Json = {
     "window": { "title": "Invalid", "width": 900, "height": 700 },
     "entry": { "kind": "html", "value": "<html></html>" },
@@ -104,19 +99,14 @@ test "load_config_manifest_from_file rebases file entry and bool debug" {
 }
 
 ///|
-test "load_config_manifest_from_file accepts explicit config filenames" {
+async test "load_config_manifest_from_file accepts explicit config filenames" {
   let loaded = load_config_manifest_from_file(
     manifest_test_path("proton.project.json"),
   )
   assert_eq(loaded.manifest().debug, 1)
 
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.create_dir("target/proton-alt-config") catch {
-    _ => ()
-  }
-  let config_path = "target/proton-alt-config/proton.dev"
+  let root = @async_fs.tmpdir(prefix="proton-alt-config-")
+  let config_path = root + "/proton.dev"
   @mbfs.write_string_to_file(
     config_path,
     (
@@ -148,14 +138,9 @@ test "load_config_manifest_from_file accepts explicit config filenames" {
 }
 
 ///|
-test "load_config_manifest_from_file rejects extension settings" {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.create_dir("target/proton-unsupported") catch {
-    _ => ()
-  }
-  let config_path = "target/proton-unsupported/proton.project.json"
+async test "load_config_manifest_from_file rejects extension settings" {
+  let root = @async_fs.tmpdir(prefix="proton-unsupported-config-")
+  let config_path = root + "/proton.project.json"
   @mbfs.write_string_to_file(
     config_path,
     (
@@ -186,39 +171,37 @@ test "load_config_manifest_from_file rejects extension settings" {
 }
 
 ///|
-test "load_config_manifest_from_file rejects unsupported top-level fields" {
+async test "load_config_manifest_from_file rejects unsupported top-level fields" {
+  let root = @async_fs.tmpdir(prefix="proton-extra-field-")
   expect_project_extra_field_error(
-    "version", "1.0.0", "Unexpected key 'version' found in proton.project.json.",
+    root, "version", "1.0.0", "Unexpected key 'version' found in proton.project.json.",
   )
   expect_project_extra_field_error(
-    "license", "MIT", "Unexpected key 'license' found in proton.project.json.",
+    root, "license", "MIT", "Unexpected key 'license' found in proton.project.json.",
   )
   expect_project_extra_field_error(
-    "description", "App", "Unexpected key 'description' found in proton.project.json.",
+    root, "description", "App", "Unexpected key 'description' found in proton.project.json.",
   )
   expect_project_extra_field_error(
+    root,
     "permissions",
     {},
     "proton.project.json.permissions must be an array",
   )
   expect_project_extra_field_error(
-    "debug", 1, "proton.project.json.debug must be a bool",
+    root, "debug", 1, "proton.project.json.debug must be a bool",
   )
 }
 
 ///|
-test "load_proton_project_config_from_file decodes tooling blocks and moon.mod metadata" {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.create_dir("target/proton-project-config") catch {
-    _ => ()
-  }
-  @mbfs.create_dir("target/proton-project-config/backend") catch {
+async test "load_proton_project_config_from_file decodes tooling blocks and moon.mod metadata" {
+  let root = @async_fs.tmpdir(prefix="proton-project-config-")
+  let backend = root + "/backend"
+  @mbfs.create_dir(backend) catch {
     _ => ()
   }
   @mbfs.write_string_to_file(
-    "target/proton-project-config/backend/moon.mod",
+    backend + "/moon.mod",
     (
       #|name = "vendor/app"
       #|version = "1.2.3"
@@ -230,7 +213,7 @@ test "load_proton_project_config_from_file decodes tooling blocks and moon.mod m
   ) catch {
     err => abort(@debug.render(Repr(err)))
   }
-  let config_path = "target/proton-project-config/proton.project.json"
+  let config_path = root + "/proton.project.json"
   @mbfs.write_string_to_file(
     config_path,
     (
@@ -301,7 +284,7 @@ test "load_proton_project_config_from_file decodes tooling blocks and moon.mod m
       #|        "role": "Editor"
       #|      }
       #|    ],
-      #|    "output": "target/proton-dist"
+      #|    "output": "custom-dist"
       #|  }
       #|}
     ),
@@ -323,10 +306,9 @@ test "load_proton_project_config_from_file decodes tooling blocks and moon.mod m
   match project.backend() {
     None => abort("expected backend config")
     Some(backend) => {
-      assert_true(
-        normalize_test_slashes(backend.path()).has_suffix(
-          "target/proton-project-config/backend",
-        ),
+      assert_eq(
+        normalize_test_slashes(backend.path()),
+        normalize_test_slashes(root + "/backend"),
       )
       assert_eq(backend.app_package(), "app")
     }
@@ -336,15 +318,13 @@ test "load_proton_project_config_from_file decodes tooling blocks and moon.mod m
     None => abort("expected frontend config")
     Some(frontend) => {
       @debug.assert_eq(frontend.dev_url(), Some("http://localhost:5173"))
-      assert_true(
-        normalize_test_slashes(frontend.dist().unwrap()).has_suffix(
-          "target/proton-project-config/frontend/dist",
-        ),
+      assert_eq(
+        normalize_test_slashes(frontend.dist().unwrap()),
+        normalize_test_slashes(root + "/frontend/dist"),
       )
-      assert_true(
-        normalize_test_slashes(frontend.path().unwrap()).has_suffix(
-          "target/proton-project-config/frontend",
-        ),
+      assert_eq(
+        normalize_test_slashes(frontend.path().unwrap()),
+        normalize_test_slashes(root + "/frontend"),
       )
       @debug.assert_eq(frontend.before_dev(), Some("npm run dev"))
       @debug.assert_eq(frontend.before_build(), Some("npm run build"))
@@ -356,29 +336,25 @@ test "load_proton_project_config_from_file decodes tooling blocks and moon.mod m
     Some(bundle) => {
       assert_true(bundle.active())
       @debug.assert_eq(bundle.targets(), ["app", "zip"])
-      assert_true(
-        normalize_test_slashes(bundle.icon()[0]).has_suffix(
-          "target/proton-project-config/icons/icon.ico",
-        ),
+      assert_eq(
+        normalize_test_slashes(bundle.icon()[0]),
+        normalize_test_slashes(root + "/icons/icon.ico"),
       )
-      assert_true(
-        normalize_test_slashes(bundle.resources()[0]).has_suffix(
-          "target/proton-project-config/resources/**",
-        ),
+      assert_eq(
+        normalize_test_slashes(bundle.resources()[0]),
+        normalize_test_slashes(root + "/resources/**"),
       )
       match bundle.sign() {
         Some(sign) =>
-          assert_true(
-            normalize_test_slashes(sign.binaries()[0]).has_suffix(
-              "target/proton-project-config/bin/worker",
-            ),
+          assert_eq(
+            normalize_test_slashes(sign.binaries()[0]),
+            normalize_test_slashes(root + "/bin/worker"),
           )
         None => fail("expected bundle sign config")
       }
-      assert_true(
-        normalize_test_slashes(bundle.output()).has_suffix(
-          "target/proton-project-config/target/proton-dist",
-        ),
+      assert_eq(
+        normalize_test_slashes(bundle.output()),
+        normalize_test_slashes(root + "/custom-dist"),
       )
 
       let targets = bundle.targets()
@@ -416,20 +392,17 @@ test "load_proton_project_config_from_file decodes tooling blocks and moon.mod m
     } else {
     abort("unexpected project summary JSON")
   }
-  assert_true(
-    normalize_test_slashes(entry_path).has_suffix(
-      "target/proton-project-config/frontend/dist/index.html",
-    ),
+  assert_eq(
+    normalize_test_slashes(entry_path),
+    normalize_test_slashes(root + "/frontend/dist/index.html"),
   )
-  assert_true(
-    normalize_test_slashes(binary_path).has_suffix(
-      "target/proton-project-config/bin/worker",
-    ),
+  assert_eq(
+    normalize_test_slashes(binary_path),
+    normalize_test_slashes(root + "/bin/worker"),
   )
-  assert_true(
-    normalize_test_slashes(output).has_suffix(
-      "target/proton-project-config/target/proton-dist",
-    ),
+  assert_eq(
+    normalize_test_slashes(output),
+    normalize_test_slashes(root + "/custom-dist"),
   )
 
   let loaded_summary = load_proton_project_summary_from_file(config_path)
@@ -462,14 +435,9 @@ test "proton project dev_manifest keeps entry when dev_url is absent" {
 }
 
 ///|
-test "load_proton_project_config_from_file validates tooling blocks" {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.create_dir("target/proton-project-invalid") catch {
-    _ => ()
-  }
-  let config_path = "target/proton-project-invalid/proton.project.json"
+async test "load_proton_project_config_from_file validates tooling blocks" {
+  let root = @async_fs.tmpdir(prefix="proton-project-invalid-")
+  let config_path = root + "/proton.project.json"
   @mbfs.write_string_to_file(
     config_path,
     (
@@ -503,14 +471,9 @@ test "load_proton_project_config_from_file validates tooling blocks" {
 }
 
 ///|
-test "load_config_manifest_from_file validates project tooling blocks" {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.create_dir("target/proton-config-manifest-invalid") catch {
-    _ => ()
-  }
-  let config_path = "target/proton-config-manifest-invalid/proton.project.json"
+async test "load_config_manifest_from_file validates project tooling blocks" {
+  let root = @async_fs.tmpdir(prefix="proton-manifest-invalid-")
+  let config_path = root + "/proton.project.json"
   @mbfs.write_string_to_file(
     config_path,
     (
@@ -544,15 +507,10 @@ test "load_config_manifest_from_file validates project tooling blocks" {
 }
 
 ///|
-test "load_proton_project_config_from_file preserves active bundle without release metadata" {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.create_dir("target/proton-project-bundle-metadata") catch {
-    _ => ()
-  }
+async test "load_proton_project_config_from_file preserves active bundle without release metadata" {
+  let root = @async_fs.tmpdir(prefix="proton-bundle-metadata-")
   @mbfs.write_string_to_file(
-    "target/proton-project-bundle-metadata/moon.mod",
+    root + "/moon.mod",
     (
       #|name = "vendor/app"
       #|version = "1.0.0"
@@ -563,7 +521,7 @@ test "load_proton_project_config_from_file preserves active bundle without relea
     err => abort(@debug.render(Repr(err)))
   }
 
-  let missing_identifier = "target/proton-project-bundle-metadata/missing-identifier.proton.project.json"
+  let missing_identifier = root + "/missing-identifier.proton.project.json"
   @mbfs.write_string_to_file(
     missing_identifier,
     (
@@ -594,14 +552,9 @@ test "load_proton_project_config_from_file preserves active bundle without relea
 }
 
 ///|
-test "load_proton_project_config_from_file validates bundle targets" {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.create_dir("target/proton-project-bundle-targets") catch {
-    _ => ()
-  }
-  let supported_target = "target/proton-project-bundle-targets/supported.proton.project.json"
+async test "load_proton_project_config_from_file validates bundle targets" {
+  let root = @async_fs.tmpdir(prefix="proton-bundle-targets-")
+  let supported_target = root + "/supported.proton.project.json"
   @mbfs.write_string_to_file(
     supported_target,
     (
@@ -631,7 +584,7 @@ test "load_proton_project_config_from_file validates bundle targets" {
   let supported = load_proton_project_config_from_file(supported_target)
   assert_eq(supported.bundle().unwrap().targets(), ["app", "zip", "dmg"])
 
-  let unsupported_target = "target/proton-project-bundle-targets/unsupported.proton.project.json"
+  let unsupported_target = root + "/unsupported.proton.project.json"
   @mbfs.write_string_to_file(
     unsupported_target,
     (
@@ -661,7 +614,7 @@ test "load_proton_project_config_from_file validates bundle targets" {
   })
   assert_eq(error.message(), "unsupported bundle.targets: msi")
 
-  let duplicate_target = "target/proton-project-bundle-targets/duplicate.proton.project.json"
+  let duplicate_target = root + "/duplicate.proton.project.json"
   @mbfs.write_string_to_file(
     duplicate_target,
     (
diff --git a/proton/bootstrap/moon.pkg b/proton/bootstrap/moon.pkg
index 2478d005..8855adde 100644
--- a/proton/bootstrap/moon.pkg
+++ b/proton/bootstrap/moon.pkg
@@ -8,6 +8,11 @@ import {
   "moonbit-community/proton/manifest",
 }
 
+import {
+  "moonbitlang/async",
+  "moonbitlang/async/fs" @async_fs,
+} for "test"
+
 warnings = "-29"
 
 supported_targets = "native"
diff --git a/proton/bootstrap/proton_project_config.mbt b/proton/bootstrap/proton_project_config.mbt
index 787a8fb4..0b1d2fcc 100644
--- a/proton/bootstrap/proton_project_config.mbt
+++ b/proton/bootstrap/proton_project_config.mbt
@@ -159,7 +159,7 @@ pub fn ProtonBundleConfig::new(
   sign? : ProtonSignConfig? = None,
   url_schemes? : Array[String] = [],
   document_types? : Array[@proton_config.ProjectDocumentType] = [],
-  output? : String = "target/proton-dist",
+  output? : String = "dist",
 ) -> ProtonBundleConfig {
   ProtonBundleConfig::{
     active,
diff --git a/proton/catalog/catalog_test.mbt b/proton/catalog/catalog_test.mbt
index b6139ad8..337f62d5 100644
--- a/proton/catalog/catalog_test.mbt
+++ b/proton/catalog/catalog_test.mbt
@@ -110,61 +110,17 @@ test "discover_extension_descriptor_files can target one extension package" {
 
 ///|
 test "load_extension_descriptor_from_file requires proton.ext.json" {
+  let path = "fixtures/rejected/extension.json"
   let error = expect_descriptor_error(() => {
-    load_extension_descriptor_from_file("target/rejected/extension.json")
+    load_extension_descriptor_from_file(path)
   })
-  assert_eq(
-    error,
-    ExtensionDescriptorError::InvalidMetadataFile(
-      path="target/rejected/extension.json",
-    ),
-  )
+  assert_eq(error, ExtensionDescriptorError::InvalidMetadataFile(path~))
 }
 
 ///|
 test "decode proton.ext.json infers MoonBit import path from nearest moon.mod" {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.create_dir("target/proton-ext-module") catch {
-    _ => ()
-  }
-  @mbfs.create_dir("target/proton-ext-module/fs") catch {
-    _ => ()
-  }
-  @mbfs.write_string_to_file(
-    "target/proton-ext-module/moon.mod",
-    (
-      #|name = "vendor/exts"
-      #|version = "2.3.4"
-      #|description = "Vendor extension pack"
-      #|license = "MIT"
-      #|repository = "https://example.com/vendor/exts"
-      #|readme = "README.md"
-      #|keywords = [ "desktop", "extension" ]
-      #|
-    ),
-    encoding="utf8",
-  ) catch {
-    err => abort(@debug.render(Repr(err)))
-  }
-  let metadata_path = "target/proton-ext-module/fs/proton.ext.json"
-  @mbfs.write_string_to_file(
-    metadata_path,
-    (
-      #|{
-      #|  "id": "vendor/fs",
-      #|  "namespace": "fs",
-      #|  "package": "@vendor/proton-fs",
-      #|  "dependencies": [
-      #|    "vendor/path"
-      #|  ]
-      #|}
-    ),
-    encoding="utf8",
-  ) catch {
-    err => abort(@debug.render(Repr(err)))
-  }
+  let root = catalog_test_path("testdata/proton-ext-module")
+  let metadata_path = root + "/fs/proton.ext.json"
   let descriptor = load_extension_descriptor_from_file(metadata_path)
   assert_eq(descriptor.id(), "vendor/fs")
   assert_eq(descriptor.version(), "2.3.4")
@@ -180,39 +136,15 @@ test "decode proton.ext.json infers MoonBit import path from nearest moon.mod" {
   @debug.assert_eq(descriptor.publish_package(), Some("@vendor/proton-fs"))
   @debug.assert_eq(descriptor.dependencies(), ["vendor/path"])
 
-  let descriptor_paths = discover_extension_descriptor_files([
-    "target/proton-ext-module/fs",
-  ])
+  let descriptor_paths = discover_extension_descriptor_files([root + "/fs"])
   assert_eq(descriptor_paths.length(), 1)
   assert_true(descriptor_paths[0].has_suffix("proton.ext.json"))
 }
 
 ///|
 test "decode proton.ext.json rejects invalid metadata" {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.create_dir("target/proton-ext-invalid") catch {
-    _ => ()
-  }
-
-  let unsupported_platform = "target/proton-ext-invalid/unsupported-platform.proton.ext.json"
-  @mbfs.write_string_to_file(
-    unsupported_platform,
-    (
-      #|{
-      #|  "id": "vendor/fs",
-      #|  "namespace": "fs",
-      #|  "platforms": [
-      #|    "windows",
-      #|    "ios"
-      #|  ]
-      #|}
-    ),
-    encoding="utf8",
-  ) catch {
-    err => abort(@debug.render(Repr(err)))
-  }
+  let root = catalog_test_path("testdata/proton-ext-invalid")
+  let unsupported_platform = root + "/unsupported-platform.proton.ext.json"
   let error = expect_descriptor_error(() => {
     load_extension_descriptor_from_file(unsupported_platform)
   })
@@ -224,22 +156,7 @@ test "decode proton.ext.json rejects invalid metadata" {
     ),
   )
 
-  let self_dependency = "target/proton-ext-invalid/self-dependency.proton.ext.json"
-  @mbfs.write_string_to_file(
-    self_dependency,
-    (
-      #|{
-      #|  "id": "vendor/fs",
-      #|  "namespace": "fs",
-      #|  "dependencies": [
-      #|    "vendor/fs"
-      #|  ]
-      #|}
-    ),
-    encoding="utf8",
-  ) catch {
-    err => abort(@debug.render(Repr(err)))
-  }
+  let self_dependency = root + "/self-dependency.proton.ext.json"
   let error = expect_descriptor_error(() => {
     load_extension_descriptor_from_file(self_dependency)
   })
@@ -251,20 +168,7 @@ test "decode proton.ext.json rejects invalid metadata" {
     ),
   )
 
-  let removed_field = "target/proton-ext-invalid/removed-field.proton.ext.json"
-  @mbfs.write_string_to_file(
-    removed_field,
-    (
-      #|{
-      #|  "id": "vendor/fs",
-      #|  "namespace": "fs",
-      #|  "spec_symbol": "extension"
-      #|}
-    ),
-    encoding="utf8",
-  ) catch {
-    err => abort(@debug.render(Repr(err)))
-  }
+  let removed_field = root + "/removed-field.proton.ext.json"
   let error = expect_descriptor_error(() => {
     load_extension_descriptor_from_file(removed_field)
   })
diff --git a/proton/catalog/testdata/proton-ext-invalid/removed-field.proton.ext.json b/proton/catalog/testdata/proton-ext-invalid/removed-field.proton.ext.json
new file mode 100644
index 00000000..d312a9f8
--- /dev/null
+++ b/proton/catalog/testdata/proton-ext-invalid/removed-field.proton.ext.json
@@ -0,0 +1,5 @@
+{
+  "id": "vendor/fs",
+  "namespace": "fs",
+  "spec_symbol": "extension"
+}
diff --git a/proton/catalog/testdata/proton-ext-invalid/self-dependency.proton.ext.json b/proton/catalog/testdata/proton-ext-invalid/self-dependency.proton.ext.json
new file mode 100644
index 00000000..592fb7ca
--- /dev/null
+++ b/proton/catalog/testdata/proton-ext-invalid/self-dependency.proton.ext.json
@@ -0,0 +1,7 @@
+{
+  "id": "vendor/fs",
+  "namespace": "fs",
+  "dependencies": [
+    "vendor/fs"
+  ]
+}
diff --git a/proton/catalog/testdata/proton-ext-invalid/unsupported-platform.proton.ext.json b/proton/catalog/testdata/proton-ext-invalid/unsupported-platform.proton.ext.json
new file mode 100644
index 00000000..8be68ebc
--- /dev/null
+++ b/proton/catalog/testdata/proton-ext-invalid/unsupported-platform.proton.ext.json
@@ -0,0 +1,8 @@
+{
+  "id": "vendor/fs",
+  "namespace": "fs",
+  "platforms": [
+    "windows",
+    "ios"
+  ]
+}
diff --git a/proton/catalog/testdata/proton-ext-module/fs/proton.ext.json b/proton/catalog/testdata/proton-ext-module/fs/proton.ext.json
new file mode 100644
index 00000000..ac905e27
--- /dev/null
+++ b/proton/catalog/testdata/proton-ext-module/fs/proton.ext.json
@@ -0,0 +1,8 @@
+{
+  "id": "vendor/fs",
+  "namespace": "fs",
+  "package": "@vendor/proton-fs",
+  "dependencies": [
+    "vendor/path"
+  ]
+}
diff --git a/proton/catalog/testdata/proton-ext-module/moon.mod b/proton/catalog/testdata/proton-ext-module/moon.mod
new file mode 100644
index 00000000..0cdc0a1f
--- /dev/null
+++ b/proton/catalog/testdata/proton-ext-module/moon.mod
@@ -0,0 +1,7 @@
+name = "vendor/exts"
+version = "2.3.4"
+description = "Vendor extension pack"
+license = "MIT"
+repository = "https://example.com/vendor/exts"
+readme = "README.md"
+keywords = [ "desktop", "extension" ]
diff --git a/proton/facade_wbtest.mbt b/proton/facade_wbtest.mbt
index cfa12e9b..73c86db3 100644
--- a/proton/facade_wbtest.mbt
+++ b/proton/facade_wbtest.mbt
@@ -1143,12 +1143,6 @@ test "entry HTML injection does not install the bridge" {
 
 ///|
 fn write_facade_dev_config(path : String, dev_url? : String) -> Unit {
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
-  @mbfs.create_dir("target/proton-facade-dev") catch {
-    _ => ()
-  }
   let config : Json = {
     "window": { "title": "Dev Test", "width": 320, "height": 240 },
     "entry": { "kind": "asset", "value": "app.html" },
@@ -1179,8 +1173,9 @@ fn restore_env_var(name : String, value : String?) -> Unit {
 }
 
 ///|
-test "implicit config path honors PROTON_CONFIG_PATH" {
-  let config_path = "target/proton-facade-dev/implicit-env.proton.project.json"
+async test "implicit config path honors PROTON_CONFIG_PATH" {
+  let root = @async_fs.tmpdir(prefix="proton-facade-config-")
+  let config_path = root + "/implicit-env.proton.project.json"
   write_facade_dev_config(config_path)
   let old_config = @env.get_env_var("PROTON_CONFIG_PATH")
   defer restore_env_var("PROTON_CONFIG_PATH", old_config)
@@ -1204,8 +1199,9 @@ test "packaged config takes precedence over environment and working directory" {
 }
 
 ///|
-test "default config API honors PROTON_CONFIG_PATH" {
-  let config_path = "target/proton-facade-dev/config-api-env.proton.project.json"
+async test "default config API honors PROTON_CONFIG_PATH" {
+  let root = @async_fs.tmpdir(prefix="proton-facade-config-")
+  let config_path = root + "/config-api-env.proton.project.json"
   write_facade_dev_config(config_path)
   let old_config = @env.get_env_var("PROTON_CONFIG_PATH")
   let old_dev = @env.get_env_var("PROTON_DEV")
@@ -1224,9 +1220,10 @@ test "default config API honors PROTON_CONFIG_PATH" {
 }
 
 ///|
-test "config API keeps non-default paths explicit" {
-  let config_path = "target/proton-facade-dev/explicit.proton.project.json"
-  let env_path = "target/proton-facade-dev/explicit-env.proton.project.json"
+async test "config API keeps non-default paths explicit" {
+  let root = @async_fs.tmpdir(prefix="proton-facade-config-")
+  let config_path = root + "/explicit.proton.project.json"
+  let env_path = root + "/explicit-env.proton.project.json"
   write_facade_dev_config(config_path)
   write_facade_dev_config(env_path)
   let old_config = @env.get_env_var("PROTON_CONFIG_PATH")
@@ -1237,8 +1234,9 @@ test "config API keeps non-default paths explicit" {
 }
 
 ///|
-test "config API overrides manifest fields and keeps base dir" {
-  let config_path = "target/proton-facade-dev/api-overrides.proton.project.json"
+async test "config API overrides manifest fields and keeps base dir" {
+  let root = @async_fs.tmpdir(prefix="proton-facade-config-")
+  let config_path = root + "/api-overrides.proton.project.json"
   write_facade_dev_config(config_path)
   let old_dev = @env.get_env_var("PROTON_DEV")
   let old_mode = @env.get_env_var("PROTON_MODE")
@@ -1273,8 +1271,9 @@ test "config API overrides manifest fields and keeps base dir" {
 }
 
 ///|
-test "dev manifest uses env override or frontend dev_url" {
-  let override_path = "target/proton-facade-dev/env-override.proton.project.json"
+async test "dev manifest uses env override or frontend dev_url" {
+  let root = @async_fs.tmpdir(prefix="proton-facade-config-")
+  let override_path = root + "/env-override.proton.project.json"
   write_facade_dev_config(override_path, dev_url="http://localhost:5173")
   let old_dev = @env.get_env_var("PROTON_DEV")
   let old_url = @env.get_env_var("PROTON_FRONTEND_URL")
@@ -1292,7 +1291,7 @@ test "dev manifest uses env override or frontend dev_url" {
     _ => fail("expected dev URL entry")
   }
 
-  let config_path = "target/proton-facade-dev/config-dev-url.proton.project.json"
+  let config_path = root + "/config-dev-url.proton.project.json"
   write_facade_dev_config(config_path, dev_url="http://localhost:5173")
   @env.unset_env_var("PROTON_FRONTEND_URL")
   let config_manifest = unwrap_configuration(() => {
@@ -1340,11 +1339,9 @@ test "single instance builder validates and resolves an inline identity" {
 }
 
 ///|
-test "launch activation classifies URLs and existing documents" {
-  let document = "target/proton-facade-activation.txt"
-  @mbfs.create_dir("target") catch {
-    _ => ()
-  }
+async test "launch activation classifies URLs and existing documents" {
+  let root = @async_fs.tmpdir(prefix="proton-facade-activation-")
+  let document = root + "/activation.txt"
   @mbfs.write_string_to_file(document, "activation", encoding="utf8") catch {
     error => abort(@debug.render(Repr(error)))
   }
@@ -1353,11 +1350,7 @@ test "launch activation classifies URLs and existing documents" {
   assert_false(launch_argument_is_url("custom:value", ["other"]))
   assert_true(launch_argument_is_document(document, ["txt"]))
   assert_false(launch_argument_is_document(document, ["md"]))
-  assert_false(
-    launch_argument_is_document("target/proton-facade-activation-missing.txt", [
-      "txt",
-    ]),
-  )
+  assert_false(launch_argument_is_document(root + "/missing.txt", ["txt"]))
 }
 
 ///|
diff --git a/proton/moon.pkg b/proton/moon.pkg
index d4f6495f..9e57f90e 100644
--- a/proton/moon.pkg
+++ b/proton/moon.pkg
@@ -21,6 +21,7 @@ import {
 }
 
 import {
+  "moonbitlang/async/fs" @async_fs,
   "moonbit-community/proton_contract",
 } for "wbtest"
 
diff --git a/proton/native_link_config.mjs b/proton/native_link_config.mjs
index a98558a2..52c80575 100644
--- a/proton/native_link_config.mjs
+++ b/proton/native_link_config.mjs
@@ -110,16 +110,15 @@ function linuxRpathLinkFlag(binDir, cc) {
   return cc.length > 0 ? `-Wl,-rpath-link,${quote(binDir)}` : "";
 }
 
-function linkFlags(dist, cc, rpathOverride) {
+function linkFlags(dist, cc) {
   const libDir = path.join(dist, "lib");
   const binDir = path.join(dist, "bin");
   if (process.platform === "win32") {
     return quote(path.join(libDir, "proton.lib"));
   }
   if (process.platform === "darwin") {
-    const rpath = rpathOverride.length > 0 ? rpathOverride : libDir;
     return appendFlags(
-      `-L${quote(libDir)} -lproton -Wl,-rpath,${quote(rpath)}`,
+      `-L${quote(libDir)} -lproton -Wl,-rpath,${quote(libDir)}`,
       darwinWarningFlags(cc),
     );
   }
@@ -129,7 +128,7 @@ function linkFlags(dist, cc, rpathOverride) {
   );
 }
 
-function linkConfig(dist, packageName, cc, rpathOverride) {
+function linkConfig(dist, packageName, cc) {
   const libDir = path.join(dist, "lib");
   const binDir = path.join(dist, "bin");
   if (process.platform === "win32") {
@@ -144,7 +143,7 @@ function linkConfig(dist, packageName, cc, rpathOverride) {
     link_flags:
       process.platform === "darwin"
         ? appendFlags(
-          `-L${quote(libDir)} -Wl,-rpath,${quote(rpathOverride.length > 0 ? rpathOverride : libDir)}`,
+          `-L${quote(libDir)} -Wl,-rpath,${quote(libDir)}`,
           darwinWarningFlags(cc),
         )
         : appendFlags(
@@ -163,19 +162,18 @@ function helperPath(binDir) {
 export function createNativeLinkConfig(env = readPayloadEnv()) {
   const rawDist = envValue(env, "PROTON_NATIVE_DIST").trim();
   const cc = envValue(env, "MOON_CC").trim();
-  const rpathOverride = envValue(env, "PROTON_PACKAGE_RPATH").trim();
   const dist = path.resolve(rawDist.length === 0 ? defaultDist() : rawDist);
   const binDir = path.join(dist, "bin");
   return {
     vars: {
-      PROTON_NATIVE_LINK_FLAGS: linkFlags(dist, cc, rpathOverride),
+      PROTON_NATIVE_LINK_FLAGS: linkFlags(dist, cc),
       PROTON_NATIVE_STUB_CC_FLAGS: "",
       PROTON_NATIVE_RUNTIME_DIR: nativeLinkPath(binDir),
       PROTON_RUNTIME_ROOT: nativeLinkPath(dist),
       PROTON_HELPER_PATH: helperPath(binDir),
     },
     link_configs: [
-      linkConfig(dist, "moonbit-community/proton/native", cc, rpathOverride),
+      linkConfig(dist, "moonbit-community/proton/native", cc),
     ],
   };
 }
diff --git a/scripts/e2e_scaffold_source_smoke.mjs b/scripts/e2e_scaffold_source_smoke.mjs
index a2ae3f45..2fb24fcb 100644
--- a/scripts/e2e_scaffold_source_smoke.mjs
+++ b/scripts/e2e_scaffold_source_smoke.mjs
@@ -241,8 +241,7 @@ function connectLocalSourceModules() {
 function verifyPackagedApp() {
   const appDir = path.join(
     projectDir,
-    "target",
-    "proton-dist",
+    "dist",
     "Todo E2E.app",
   );
   assert(fs.existsSync(appDir), `packaged app is missing: ${appDir}`);
diff --git a/scripts/macos_package_smoke.mjs b/scripts/macos_package_smoke.mjs
index f4dd8f90..b9cb03f7 100644
--- a/scripts/macos_package_smoke.mjs
+++ b/scripts/macos_package_smoke.mjs
@@ -12,7 +12,15 @@ const exampleName = "47_dev_extension_js";
 const productName = "Proton Dev Extension JS";
 const executableName = "proton-dev-extension-js";
 const exampleDir = path.join(repoRoot, "examples", exampleName);
-const distDir = path.join(exampleDir, "target", "proton-dist");
+const exampleModule = fs.readFileSync(
+  path.join(repoRoot, "examples", "moon.mod"),
+  "utf8",
+);
+const exampleVersion = exampleModule.match(/^version\s*=\s*"([^"]+)"/m)?.[1];
+if (!exampleVersion) {
+  throw new Error("examples/moon.mod is missing version");
+}
+const distDir = path.join(exampleDir, "dist");
 const appPath = path.join(distDir, `${productName}.app`);
 const archivePath = `${appPath}.zip`;
 const helperNames = [
@@ -317,8 +325,8 @@ function verifyBundle() {
   const infoPlist = path.join(contents, "Info.plist");
   const plistExpectations = new Map([
     ["CFBundleIdentifier", "com.justjavac.proton.dev-extension-js"],
-    ["CFBundleShortVersionString", "0.1.0"],
-    ["CFBundleVersion", "0.1.0"],
+    ["CFBundleShortVersionString", exampleVersion],
+    ["CFBundleVersion", exampleVersion],
   ]);
   for (const [key, expected] of plistExpectations) {
     const actual = run(
diff --git a/scripts/windows_package_smoke.ps1 b/scripts/windows_package_smoke.ps1
index 6fd2ade7..fe4e45e1 100644
--- a/scripts/windows_package_smoke.ps1
+++ b/scripts/windows_package_smoke.ps1
@@ -7,7 +7,7 @@ $ExampleName = "47_dev_extension_js"
 $ProductName = "Proton Dev Extension JS"
 $ExecutableName = "proton-dev-extension-js"
 $ExampleDir = Join-Path $RepoRoot (Join-Path "examples" $ExampleName)
-$DistDir = Join-Path $ExampleDir "target\proton-dist"
+$DistDir = Join-Path $ExampleDir "dist"
 $PortableDir = Join-Path $DistDir $ExecutableName
 $ArchivePath = Join-Path $DistDir ($ExecutableName + ".zip")
 $CdpTimeoutSeconds = 45

From 49529c2728bc18fbb436e98161e38ac084152376 Mon Sep 17 00:00:00 2001
From: Milky2018 <842376130@qq.com>
Date: Thu, 13 Aug 2026 12:01:10 +0800
Subject: [PATCH 2/2] fix(e2e): use configured backend package

---
 e2e/test/dev_extension_process_wbtest.mbt | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/e2e/test/dev_extension_process_wbtest.mbt b/e2e/test/dev_extension_process_wbtest.mbt
index 3a8c6df4..cd74b928 100644
--- a/e2e/test/dev_extension_process_wbtest.mbt
+++ b/e2e/test/dev_extension_process_wbtest.mbt
@@ -261,8 +261,6 @@ async fn spawn_dev_extension_cli_app(
     "dev",
     "--config",
     "examples/47_dev_extension_js/proton.project.json",
-    "--package",
-    ".",
     "--moon-target-dir",
     dev_extension_app_target_dir(output_root, "dev", cdp_port),
     "--url",
@@ -374,8 +372,6 @@ async fn build_dev_extension_frontend(
       "build",
       "--config",
       "examples/47_dev_extension_js/proton.project.json",
-      "--package",
-      ".",
       "--moon-target-dir",
       app_target_dir,
     ],