diff --git a/backend/mpc-system/docker-compose.yml b/backend/mpc-system/docker-compose.yml
index 438486e9..a892a7b5 100644
--- a/backend/mpc-system/docker-compose.yml
+++ b/backend/mpc-system/docker-compose.yml
@@ -252,6 +252,8 @@ services:
       MPC_CRYPTO_MASTER_KEY: ${CRYPTO_MASTER_KEY}
       # API 认证密钥 (与 mpc-service 配置的 MPC_API_KEY 一致)
       MPC_API_KEY: ${MPC_API_KEY}
+      # Party identity for Message Router registration
+      PARTY_ID: delegate-party
     depends_on:
       session-coordinator:
         condition: service_healthy