Update app_environment.py

app_environment.py

@@ -33,4 +33,9 @@ def remove_session_directory(directory, root):
 
 
 def hosted_download_limit():
-    return 4_000_000_000 if hosted_mode() else None
+    if not hosted_mode():
+        return None
+    gigabytes = int(os.environ.get('TOKEN_VISUALISER_MAX_DOWNLOAD_GB', '16'))
+    if gigabytes < 1:
+        raise ValueError('TOKEN_VISUALISER_MAX_DOWNLOAD_GB must be a positive integer.')
+    return gigabytes * 1_000_000_000