diff --git a/tools/syntax_sanity.py b/tools/syntax_sanity.py
new file mode 100644
index 0000000..cf12fc6
--- /dev/null
+++ b/tools/syntax_sanity.py
@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+"""Rough brace/paren balance sanity check for edited C++ files."""
+import os
+import re
+import sys
+
+os.chdir(os.path.join(os.path.dirname(os.path.abspath(__file__)),
+                      "..", "terminal", "kiosk-shell"))
+
+FILES = [
+    "src/main_window.cpp",
+    "src/main_window.h",
+    "src/desktop_list_page.cpp",
+    "src/desktop_list_page.h",
+    "src/desktop_service.cpp",
+    "src/desktop_service.h",
+    "src/desktop_session.h",
+    "src/moonlight_session.cpp",
+    "src/moonlight_session.h",
+    "src/login_page.cpp",
+    "src/login_page.h",
+    "src/state_machine.cpp",
+    "src/state_machine.h",
+]
+
+fail = False
+for f in FILES:
+    src = open(f, encoding="utf-8").read()
+    src2 = re.sub(r"//[^\n]*", "", src)
+    src2 = re.sub(r'"(?:\\.|[^"\\])*"', '""', src2)
+    src2 = re.sub(r"'(?:\\.|[^'\\])*'", "''", src2)
+    counts = {c: src2.count(c) for c in "{}()"}
+    ok = counts["{"] == counts["}"] and counts["("] == counts[")"]
+    print(f, counts, "OK" if ok else "MISMATCH")
+    if not ok:
+        fail = True
+
+sys.exit(1 if fail else 0)