fix(): fixed bugs with cache invalidation, notifications and guardrails

src/backend/apps/notifications/services.py

@@ -200,15 +200,24 @@ def _build_event_key(
     return f"{event_type}:{payload.experiment_id}:{bucket}"
 
 
+def _escape_markdown(text: str) -> str:
+    for ch in r"\_*[]()~`>#+-=|{}.!":
+        text = text.replace(ch, f"\\{ch}")
+    return text
+
+
 def _send_telegram(config: dict[str, Any], payload: dict[str, Any]) -> None:
     bot_token = config.get("bot_token", "")
     chat_id = config.get("chat_id", "")
     if not bot_token or not chat_id:
         raise ValueError("Telegram config requires 'bot_token' and 'chat_id'.")
 
-    text = f"*{payload['title']}*\n\n{payload['body']}"
+    title = _escape_markdown(payload["title"])
+    body = _escape_markdown(payload["body"])
+    text = f"*{title}*\n\n{body}"
     if payload.get("experiment_name"):
-        text += f"\n\nExperiment: {payload['experiment_name']}"
+        name = _escape_markdown(payload["experiment_name"])
+        text += f"\n\nExperiment: {name}"
 
     api_url = config.get(
         "api_url",
@@ -219,7 +228,7 @@ def _send_telegram(config: dict[str, Any], payload: dict[str, Any]) -> None:
         json={
             "chat_id": chat_id,
             "text": text,
-            "parse_mode": "Markdown",
+            "parse_mode": "MarkdownV2",
         },
         timeout=10,
     )
@@ -249,7 +258,7 @@ def _send_smtp(config: dict[str, Any], payload: dict[str, Any]) -> None:
 def flush_pending_notifications() -> dict[str, int]:
     pending = NotificationLog.objects.filter(
         status=NotificationStatus.PENDING,
-    ).select_related("channel")
+    ).select_related("channel").order_by("created_at")
 
     senders = {
         ChannelType.TELEGRAM: _send_telegram,