diff --git a/packaging/README.md b/packaging/README.md
index ed7f165..2045204 100644
--- a/packaging/README.md
+++ b/packaging/README.md
@@ -20,7 +20,7 @@ Zip packages are **not** published. Releases ship **Setup.exe only**.
 
 **Installer:** English + 简体中文 (language dialog). Icons use `packaging/assets/netx.ico`.
 
-**Offline:** Setup ships portable PostgreSQL, **`python/runtime` + `.venv`** (portable; not tied to the build PC’s user profile), and WinSW. **First install** shows the Database page (built-in or external PostgreSQL; external credentials validated with `psql SELECT 1`). **Re-running Setup when `%ProgramData%\NetX\.env` has `NETX_DB_MODE` or a non-empty legacy `NETX_DATABASE_URL`** skips the DB wizard by default. Update stops and resumes an installed Windows service or startup task while replacing files. Service install uses bundled WinSW. Auto-update still needs network later, and is unchecked by default.
+**Offline:** Setup ships portable PostgreSQL, **`python/runtime` + `.venv`** (portable; not tied to the build PC’s user profile), and WinSW. On upgrade, Setup removes the old runtime and virtual environment before copying the bundled pair, preventing stale standard-library files when Python versions have different layouts. **First install** shows the Database page (built-in or external PostgreSQL; external credentials validated with `psql SELECT 1`). **Re-running Setup when `%ProgramData%\NetX\.env` has `NETX_DB_MODE` or a non-empty legacy `NETX_DATABASE_URL`** skips the DB wizard by default. Update stops and resumes an installed Windows service or startup task while replacing files. Service install uses bundled WinSW. Auto-update still needs network later, and is unchecked by default.
 
 **OS:** Windows 10/11 or Windows Server **2016+** recommended. Packaging scripts are UTF-8 **with BOM** so Chinese UI works on Windows PowerShell 5.x. The Windows release workflow pins bundled Python to **3.12**, so local release builds should use the same version for consistent artifacts.
 
diff --git a/packaging/build_release.ps1 b/packaging/build_release.ps1
index 0451b2b..4a83bea 100644
--- a/packaging/build_release.ps1
+++ b/packaging/build_release.ps1
@@ -210,6 +210,8 @@ if ($CreateVenv) {
     if (-not (Test-NetxVenvRunnable -VenvPython $venvPy)) {
         throw "venv_not_runnable_after_build: check python/runtime copy"
     }
+    & $venvPy -c "from pathlib import Path; import glob; print(Path.cwd()); print(glob.__file__)"
+    if ($LASTEXITCODE -ne 0) { throw "python_stdlib_smoke_failed: pathlib/glob import mismatch" }
 
     & $venvPy -m pip install --upgrade pip
     & $venvPy -m pip install -r (Join-Path $stage "requirements.txt")
@@ -219,6 +221,8 @@ if ($CreateVenv) {
     if (-not (Test-NetxVenvRunnable -VenvPython $venvPy)) {
         throw "venv_not_runnable_after_pip"
     }
+    & $venvPy -c "from pathlib import Path; import glob; print(Path.cwd()); print(glob.__file__)"
+    if ($LASTEXITCODE -ne 0) { throw "python_stdlib_smoke_failed_after_pip: pathlib/glob import mismatch" }
 
     Write-Host "==> Slimming .venv (drop tests / __pycache__ / *.pyc)"
     $site = Join-Path $stage ".venv\Lib\site-packages"
diff --git a/packaging/installer/netx.iss b/packaging/installer/netx.iss
index 0f43470..49f0777 100644
--- a/packaging/installer/netx.iss
+++ b/packaging/installer/netx.iss
@@ -5,7 +5,7 @@
 
 #define MyAppName "NetX"
 #ifndef MyAppVersion
-  #define MyAppVersion "0.4.14"
+  #define MyAppVersion "0.4.15"
 #endif
 #define MyAppPublisher "NetX"
 #define MyAppURL "https://github.com/hansjone/netx"
@@ -154,6 +154,11 @@ Name: "{commonappdata}\NetX\pgdata"; Permissions: users-modify
 Name: "{commonappdata}\NetX\backups"; Permissions: users-modify
 
 [InstallDelete]
+; Python minor releases can change stdlib layout (for example pathlib.py -> pathlib\\).
+; Remove the previous runtime and venv before copying the new ones so an upgrade
+; cannot leave orphaned modules that shadow files from the shipped Python version.
+Type: filesandordirs; Name: "{app}\python\runtime"
+Type: filesandordirs; Name: "{app}\.venv"
 ; Remove legacy desktop shortcuts from older Setup builds (keep a single NetX icon).
 Type: files; Name: "{commondesktop}\NetX Start.lnk"
 Type: files; Name: "{commondesktop}\NetX First-time setup.lnk"
diff --git a/packaging/manifest.example.json b/packaging/manifest.example.json
index ab97808..78d01c5 100644
--- a/packaging/manifest.example.json
+++ b/packaging/manifest.example.json
@@ -1,11 +1,11 @@
 {
   "channel": "stable",
-  "latest": "0.4.14",
+  "latest": "0.4.15",
   "min_compatible": "0.3.0",
-  "notes_url": "https://github.com/hansjone/netx/releases/tag/v0.4.14",
+  "notes_url": "https://github.com/hansjone/netx/releases/tag/v0.4.15",
   "windows": {
-    "url": "https://github.com/hansjone/netx/releases/download/v0.4.14/NetX-Setup-0.4.14.exe",
-    "setup_url": "https://github.com/hansjone/netx/releases/download/v0.4.14/NetX-Setup-0.4.14.exe",
+    "url": "https://github.com/hansjone/netx/releases/download/v0.4.15/NetX-Setup-0.4.15.exe",
+    "setup_url": "https://github.com/hansjone/netx/releases/download/v0.4.15/NetX-Setup-0.4.15.exe",
     "package": "setup",
     "sha256": "",
     "size": 0
diff --git a/pyproject.toml b/pyproject.toml
index 7f924ce..573a8de 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "netx-ops"
-version = "0.4.14"
+version = "0.4.15"
 description = "netx operations tool: alarm-centric workflows with REST API and stdio MCP"
 readme = "README.md"
 requires-python = ">=3.11"