diff --git a/.env.example b/.env.example
index 2eac0dc2d..1e5d41d49 100644
--- a/.env.example
+++ b/.env.example
@@ -37,6 +37,11 @@ NEXT_PUBLIC_BRAND_NAME="Clowder AI"
 REDIS_PORT=6399
 REDIS_URL=redis://localhost:6399
 
+# Message TTL (seconds). Default is 7 days — messages auto-expire!
+# Set to 0 for permanent storage (recommended).
+# 消息存储 TTL（秒）。默认 7 天，消息会过期删除！设为 0 = 永久保存。
+MESSAGE_TTL_SECONDS=0
+
 # ── Model API Keys 模型密钥（按需填写）────────────────────────
 # Only needed if calling model APIs directly. If you use Claude Code CLI
 # subscription, the CLI manages auth for you — no key needed here.