diff --git a/src/server.ts b/src/server.ts
index fdfb429..706ac6e 100644
--- a/src/server.ts
+++ b/src/server.ts
@@ -3,6 +3,7 @@ import { CommandService } from './services/command';
 import { GroupSyncService } from './services/group-sync';
 import { ResponseQueue } from './services/response-queue';
 import { WebhookManager } from './services/webhook-manager';
+import { normalizeWhatsAppId } from './utils/whatsapp';
 
 // Bun is available globally when running under Bun runtime
 declare global {
@@ -107,6 +108,15 @@ export class WebhookServer {
 			return;
 		}
 
+		// Normalize sender ID for consistency and validation
+		const normalizedSenderId = normalizeWhatsAppId(data.key.participant);
+		if (!normalizedSenderId) {
+			if (process.env.NODE_ENV !== 'test') {
+				console.log('⚠️ Invalid sender ID, ignoring message');
+			}
+			return;
+		}
+
 		// Forward to command service only if:
 		// 1. It's a text message (has conversation field)
 		// 2. Starts with /tarea command