diff --git a/scripts/prepare-runtime-bundle.mjs b/scripts/prepare-runtime-bundle.mjs
index e5bc332..584cf84 100644
--- a/scripts/prepare-runtime-bundle.mjs
+++ b/scripts/prepare-runtime-bundle.mjs
@@ -2,10 +2,23 @@
 import fs from 'node:fs/promises'
 import path from 'node:path'
 import { spawnSync } from 'node:child_process'
+import { setTimeout as delay } from 'node:timers/promises'
 import sevenZip from '7zip-bin'
 import { transformRuntime } from './runtime-transform.mjs'
 import { projectRoot, runtimeRoot, manifest, digest, inventory, verifyRuntimeBundle } from './runtime-bundle.mjs'
 const cache = path.join(projectRoot, '.tmp/runtime-downloads')
+async function renameExtractedDirectory(source, destination) {
+  for (let attempt = 0; ; attempt += 1) {
+    try {
+      await fs.rename(source, destination)
+      return
+    } catch (error) {
+      // Windows scanners can briefly hold freshly extracted executables open.
+      if (process.platform !== 'win32' || !['EPERM', 'EACCES', 'EBUSY'].includes(error.code) || attempt >= 9) throw error
+      await delay(100 * (attempt + 1))
+    }
+  }
+}
 await fs.mkdir(cache, { recursive: true })
 const stage = await fs.mkdtemp(path.join(runtimeRoot, '.prepare-'))
 try {
@@ -26,7 +39,7 @@ try {
     const result = spawnSync(sevenZip.path7za, ['x', archive, `-o${unpack}`, '-y'], { encoding: 'utf8', windowsHide: true })
     if (result.error || result.status !== 0) throw new Error(`Archive extraction failed: ${runtime.id}: ${result.error || result.stderr || result.stdout}`)
     const target = path.join(stage, runtime.id)
-    await fs.rename(path.join(unpack, runtime.prefix), target)
+    await renameExtractedDirectory(path.join(unpack, runtime.prefix), target)
     await transformRuntime(runtime.id, target)
     // No loose mutation of the extraction lock. A source update requires reviewed tree digest changes.
     const tree = digest(JSON.stringify(await inventory(target)))
diff --git a/scripts/smoke-runtime-bundle.mjs b/scripts/smoke-runtime-bundle.mjs
index a11d98f..52ef1ee 100644
--- a/scripts/smoke-runtime-bundle.mjs
+++ b/scripts/smoke-runtime-bundle.mjs
@@ -17,17 +17,17 @@ try {
     npm_config_userconfig: path.join(temp, 'npmrc'), npm_config_globalconfig: path.join(temp, 'npm-globalrc'),
     npm_config_cache: path.join(temp, 'npm-cache'), npm_config_prefix: path.join(temp, 'npm-prefix'),
     PYTHONUSERBASE: path.join(temp, 'python-user'), PIP_CACHE_DIR: path.join(temp, 'pip-cache'),
-    PYTHONNOUSERSITE: '1', GIT_CONFIG_NOSYSTEM: '1', GIT_CONFIG_GLOBAL: path.join(temp, 'gitconfig'),
+    PYTHONNOUSERSITE: '1', PYTHONDONTWRITEBYTECODE: '1', GIT_CONFIG_NOSYSTEM: '1', GIT_CONFIG_GLOBAL: path.join(temp, 'gitconfig'),
     PATH: [path.join(root, 'node'), path.join(root, 'python'), path.join(root, 'git/cmd'), path.join(root, 'git/bin'), path.join(process.env.SystemRoot || 'C:\\Windows', 'System32')].join(';') }
-  const run = (exe, args) => {
-    const r = spawnSync(exe, args, { cwd: temp, env, encoding: 'utf8', timeout: 60_000, windowsHide: true })
+  const run = (exe, args, options = {}) => {
+    const r = spawnSync(exe, args, { cwd: temp, env, encoding: 'utf8', timeout: 60_000, windowsHide: true, ...options })
     if (r.error || r.status !== 0) throw new Error(`${exe} ${args.join(' ')} failed: ${r.error || r.stderr || r.stdout}`)
     console.log(r.stdout.trim())
   }
   const node = path.join(root, 'node/node.exe'), python = path.join(root, 'python/python.exe')
   run(node, ['--version'])
   // Explicit cmd.exe, fixed arguments only; downloaded npm/npx scripts never use shell interpolation from user input.
-  for (const command of ['npm', 'npx']) run(process.env.ComSpec || 'cmd.exe', ['/d', '/s', '/c', `""${path.join(root, `node/${command}.cmd`)}" --version"`])
+  for (const command of ['npm', 'npx']) run(process.env.ComSpec || 'cmd.exe', ['/d', '/s', '/c', `""${path.join(root, `node/${command}.cmd`)}" --version"`], { windowsVerbatimArguments: true })
   run(python, ['--version']); run(python, ['-m', 'pip', '--version'])
   run(python, ['-m', 'venv', path.join(temp, 'venv')])
   run(path.join(temp, 'venv/Scripts/python.exe'), ['-m', 'pip', '--version'])