diff --git a/build-windows-base.sh b/build-windows-base.sh
index 4288708..a567444 100755
--- a/build-windows-base.sh
+++ b/build-windows-base.sh
@@ -31,6 +31,8 @@ set -euo pipefail
 
 images_dir="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)"
 downloader="${images_dir}/download-images.sh"
+# Path lookups below must not offer to run this script again.
+export VM_IMAGE_NO_PROMPT=1
 win_dir="${images_dir}/windows11"
 
 usage() {
@@ -116,6 +118,17 @@ if ((!from_img)); then
     || die "install socat or nc (it presses a key at the boot prompt of the ISO)."
 fi
 
+# Without the ISO, offer to download it (needs a terminal).
+if [[ -z "${WIN11_VM_INSTALL_ISO:-}" ]] && ! "$downloader" --print-path windows11 --iso >/dev/null 2>&1; then
+  "$downloader" --print-path windows11 --iso >&2 || true
+  if { : </dev/tty >/dev/tty; } 2>/dev/null; then
+    printf 'Download the Windows 11 ISO now? [y/N] ' >/dev/tty
+    read -r answer </dev/tty || answer=
+    [[ "$answer" == [yY] || "$answer" == [yY][eE][sS] ]] || exit 1
+    "$downloader" windows11 || exit 1
+  fi
+fi
+
 output="${output:-$("$downloader" --print-path windows11)}"
 if [[ -e "$output" && $force -eq 0 ]]; then
   die "${output} exists (it may be the backing file of existing VM disks); use --force or another OUTPUT."
diff --git a/download-images.sh b/download-images.sh
index f4c6820..139364d 100755
--- a/download-images.sh
+++ b/download-images.sh
@@ -156,6 +156,36 @@ The Windows ISO is found automatically in install-iso/ by matching
 EOF
 }
 
+# Ask a yes/no question on the terminal; fails when there is none or the answer
+# is not yes. stdout carries the printed path, so all dialogue goes to /dev/tty.
+ask_yes_no() {
+  local answer
+  { : </dev/tty >/dev/tty; } 2>/dev/null || return 1
+  printf '%s [y/N] ' "$1" >/dev/tty
+  read -r answer </dev/tty || return 1
+  [[ "$answer" == [yY] || "$answer" == [yY][eE][sS] ]]
+}
+
+# Print the base QCOW2 path. When the image does not exist and a terminal is
+# attached, offer to run build-windows-base.sh, which in turn offers to download
+# the ISO. The builder sets VM_IMAGE_NO_PROMPT so its own lookups never ask.
+windows_base_path() {
+  local qcow2 builder="${images_dir}/build-windows-base.sh"
+  if qcow2="$(windows_qcow2_path 2>/dev/null)" && [[ -f "$qcow2" ]]; then
+    printf '%s\n' "$qcow2"
+    return 0
+  fi
+  windows_qcow2_path >/dev/null || true
+  if [[ -z "${VM_IMAGE_NO_PROMPT:-}" && -x "$builder" ]] && ask_yes_no "Build the Windows 11 base image now with build-windows-base.sh?"; then
+    # stdout carries the path, so the build's output goes to the terminal.
+    "$builder" >/dev/tty 2>&1 </dev/tty || return 1
+    windows_qcow2_path
+    return
+  fi
+  # Name the expected path if the ISO fixes it; the caller reports it missing.
+  windows_qcow2_path 2>/dev/null
+}
+
 print_image_path() {
   local target="$1"
   local media="${2:-qcow2}"
@@ -171,7 +201,7 @@ print_image_path() {
       if [[ "$media" == iso ]]; then
         windows_iso_path
       else
-        windows_qcow2_path
+        windows_base_path
       fi
       ;;
     *)
@@ -416,7 +446,27 @@ download_windows_iso() {
     printf 'Error: node is required to get the Windows 11 ISO URL.\n' >&2
     exit 1
   fi
-  url="$(node "${images_dir}/nodejs/get-windows-iso-url.js" --arch "$windows_arch")"
+  if [[ ! -d "${images_dir}/nodejs/node_modules/playwright-core" ]]; then
+    printf 'Error: the Node.js dependencies are not installed (npm ci has not been run in %s/nodejs).\n' \
+      "$images_dir" >&2
+    command -v npm >/dev/null 2>&1 || { printf 'Error: npm is required; install Node.js with npm.\n' >&2; exit 1; }
+    ask_yes_no "Run npm ci in ${images_dir}/nodejs now?" || exit 1
+    (cd "${images_dir}/nodejs" && npm ci) || exit 1
+  fi
+  local status=0
+  url="$(node "${images_dir}/nodejs/get-windows-iso-url.js" --arch "$windows_arch")" || status=$?
+  if ((status == 2)) && [[ -z "${CHROME_PATH:-}" ]]; then
+    # Exit status 2 means Chromium was not found (the script has said so).
+    ask_yes_no "Install Chromium with playwright-core now?" || exit 1
+    # Default to the npmmirror mirror (the official CDN is slow in China); set
+    # PLAYWRIGHT_DOWNLOAD_HOST to override it.
+    (cd "${images_dir}/nodejs" \
+      && PLAYWRIGHT_DOWNLOAD_HOST="${PLAYWRIGHT_DOWNLOAD_HOST:-https://cdn.npmmirror.com/binaries/playwright}" \
+        npx playwright-core install chromium) || exit 1
+    url="$(node "${images_dir}/nodejs/get-windows-iso-url.js" --arch "$windows_arch")" || exit 1
+  elif ((status != 0)); then
+    exit "$status"
+  fi
   [[ -n "$url" ]] || { printf 'Error: no Windows 11 ISO URL.\n' >&2; exit 1; }
   name="${url%%\?*}"
   name="${name##*/}"
diff --git a/nodejs/get-windows-iso-url.js b/nodejs/get-windows-iso-url.js
index d69e280..807eb16 100755
--- a/nodejs/get-windows-iso-url.js
+++ b/nodejs/get-windows-iso-url.js
@@ -5,12 +5,11 @@
 // Usage: node get-windows-iso-url.js [--arch x64|arm64] [--lang NAME]
 // Environment:
 //   PLAYWRIGHT_CORE  playwright-core directory (default: node_modules here)
-//   CHROME_PATH      Chromium executable (default: newest one in ~/.cache/ms-playwright)
+//   CHROME_PATH      Chromium executable (default: the one Playwright installed)
 // The URL expires after about 24 hours and may be bound to the IP that
 // requested it. Only the URL goes to stdout; logs go to stderr.
 
 const fs = require('fs');
-const os = require('os');
 const path = require('path');
 
 const args = process.argv.slice(2);
@@ -28,8 +27,7 @@ Options:
 
 Environment:
   PLAYWRIGHT_CORE      playwright-core directory (default: node_modules here)
-  CHROME_PATH          Chromium executable (default: newest one in
-                       ~/.cache/ms-playwright)
+  CHROME_PATH          Chromium executable (default: the one Playwright installed)
 
 Examples:
   node get-windows-iso-url.js --arch x64 --lang "Chinese Simplified"
@@ -60,17 +58,20 @@ function findPlaywright() {
   process.exit(2);
 }
 
-function findChrome() {
-  if (process.env.CHROME_PATH) return process.env.CHROME_PATH;
-  const root = path.join(os.homedir(), '.cache/ms-playwright');
-  const dirs = fs.existsSync(root) ? fs.readdirSync(root).filter(d => /^chromium-\d+$/.test(d)).sort() : [];
-  if (!dirs.length) { console.error('Chromium not found: set CHROME_PATH or run npx playwright-core install chromium'); process.exit(2); }
-  return path.join(root, dirs.pop(), 'chrome-linux64/chrome');
+// CHROME_PATH wins; otherwise Playwright picks the Chromium it installed (in
+// its own per-OS cache, PLAYWRIGHT_BROWSERS_PATH if set).
+function launchOptions(chromium) {
+  if (process.env.CHROME_PATH) return { executablePath: process.env.CHROME_PATH, headless: true };
+  if (!fs.existsSync(chromium.executablePath())) {
+    console.error('Chromium not found: set CHROME_PATH or run npx playwright-core install chromium');
+    process.exit(2);
+  }
+  return { headless: true };
 }
 
 (async () => {
   const { chromium } = require(findPlaywright());
-  const browser = await chromium.launch({ executablePath: findChrome(), headless: true });
+  const browser = await chromium.launch(launchOptions(chromium));
   try {
     const ctx = await browser.newContext({
       locale: 'en-US',