diff --git a/agent_service/agents/master_agent.py b/agent_service/agents/master_agent.py
index d2e4acd..c8a8334 100644
--- a/agent_service/agents/master_agent.py
+++ b/agent_service/agents/master_agent.py
@@ -67,7 +67,9 @@ class MasterAgent:
         template = _load_prompt('master_system.txt')
         agent_list = chr(10).join(
             f'- {a["agent_key"]}: {a["capabilities_summary"]}' for a in active_agents)
-        return template.format(agent_list=agent_list)
+        # Plain substitution — the template contains literal { } from a JSON
+        # example block, so str.format would treat them as fields.
+        return template.replace('{agent_list}', agent_list)
 
     async def handle_message(self, user_id, channel_id, message, directive_id) -> MasterResponse:
         try: