diff --git a/scripts/get-assets.sh b/scripts/get-assets.sh
index 863b226d3..7128ab4c9 100755
--- a/scripts/get-assets.sh
+++ b/scripts/get-assets.sh
@@ -15,6 +15,30 @@ TMP_DIR="$HOME/GeneralsX/.steamcmd_zh"
 
 mkdir -p "$TMP_DIR" "$DEST"
 
+# macOS Gatekeeper quarantines steamcmd's unnotarized bundled frameworks
+# (e.g. Breakpad.framework) when Homebrew installs the cask. On first run that
+# pops a blocking "Apple could not verify ... malware" dialog that stops
+# steamcmd dead. Clear the quarantine flag off the steamcmd install up front.
+if [[ "$(uname)" == "Darwin" ]] && command -v brew >/dev/null 2>&1; then
+    STEAMCMD_CASK="$(brew --prefix)/Caskroom/steamcmd"
+    [[ -d "$STEAMCMD_CASK" ]] && xattr -dr com.apple.quarantine "$STEAMCMD_CASK" 2>/dev/null || true
+fi
+
+# steamcmd and the Steam desktop client share one data directory
+# (~/Library/Application Support/Steam on macOS, ~/.steam on Linux). When the
+# desktop client is running it holds a single-instance lock, so steamcmd stalls
+# forever right after printing "Verifying installation..." — no error, just a
+# silent hang. Fail fast with an actionable message instead.
+if pgrep -x steam_osx >/dev/null 2>&1 \
+    || pgrep -f 'Steam.AppBundle' >/dev/null 2>&1 \
+    || pgrep -x steam >/dev/null 2>&1; then
+    echo "Error: the Steam desktop client is running." >&2
+    echo "steamcmd shares Steam's data directory, and the running client locks it —" >&2
+    echo 'steamcmd would hang forever after "Verifying installation...".' >&2
+    echo "Quit Steam completely (Steam > Quit Steam, or Cmd-Q on macOS), then re-run this script." >&2
+    exit 1
+fi
+
 # App 2732960 = C&C Generals Zero Hour (Windows depot; assets are platform-independent)
 steamcmd \
     +@sSteamCmdForcePlatformType windows \