diff --git a/packages/services/agent-service/src/infrastructure/engines/claude-agent-sdk/claude-agent-sdk-engine.ts b/packages/services/agent-service/src/infrastructure/engines/claude-agent-sdk/claude-agent-sdk-engine.ts
index 3f22add..5205cc3 100644
--- a/packages/services/agent-service/src/infrastructure/engines/claude-agent-sdk/claude-agent-sdk-engine.ts
+++ b/packages/services/agent-service/src/infrastructure/engines/claude-agent-sdk/claude-agent-sdk-engine.ts
@@ -174,7 +174,7 @@ export class ClaudeAgentSdkEngine implements AgentEnginePort {
 
         while (eventQueue.length > 0) {
           const event = eventQueue.shift();
-          if (event === null) return;
+          if (event === null || event === undefined) return;
           yield event;
         }
       }