diff --git a/requirements.txt b/requirements.txt
index ee2b572..5b0e2a3 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,6 +7,9 @@ cryptography>=41.0.0
 # Optional: HTTP/2 multiplexing (faster apps_script relay)
 h2>=4.1.0
 
+# Optional: CA bundle for TLS verification (recommended on macOS / Windows)
+certifi>=2024.1.0
+
 # Optional: Brotli decompression (modern websites send `br` encoding)
 brotli>=1.1.0