diff --git a/agentclaw/app/agent_claw_main/main.py b/agentclaw/app/agent_claw_main/main.py
index e4b26cf..b591f10 100644
--- a/agentclaw/app/agent_claw_main/main.py
+++ b/agentclaw/app/agent_claw_main/main.py
@@ -563,9 +563,21 @@ async def main(payload: dict, context):
         tools=all_tools,
     )
 
+    # Intercept heartbeat: replace bare [HEARTBEAT] with a strict-format instruction.
+    # Agent-runner suppresses replies that start with HEARTBEAT_OK, so only real alerts reach Telegram.
+    prompt = payload.get('prompt', '')
+    if prompt.strip() == '[HEARTBEAT]':
+        prompt = (
+            'HEARTBEAT CHECK: Silently check for anything urgent Daniel should know about '
+            '(calendar events starting within 2 hours, unread urgent emails, overdue reminders). '
+            'Do NOT narrate your checking process. '
+            'If nothing is urgent: reply with the single word HEARTBEAT_OK and nothing else. '
+            'If something IS urgent: reply with 2-3 lines max summarising only the urgent items.'
+        )
+
     final_message = None
     try:
-        async for event in agent.stream_async(payload.get('prompt', '')):
+        async for event in agent.stream_async(prompt):
             if 'result' in event:
                 final_message = event['result'].message
             yield event