diff --git a/lib/frpc.js b/lib/frpc.js
index 54d0d31..1d4ed81 100644
--- a/lib/frpc.js
+++ b/lib/frpc.js
@@ -121,8 +121,7 @@ async function startTtyd() {
     const shell = fs.existsSync('/bin/bash') ? '/bin/bash' : '/bin/sh';
     // 以普通用户身份启动 shell（与 SSH 登录一致）
     const ttydUser = process.env.CLAWD_TTY_USER || 'sts';
-    const loginCmd = `/bin/su - ${ttydUser}`;
-    const proc = spawn(TTYD_BIN, ['-p', String(TTYD_PORT), '-i', '127.0.0.1', '-W', '-t', 'cursorBlink=true', loginCmd], {
+    const proc = spawn(TTYD_BIN, ['-p', String(TTYD_PORT), '-i', '127.0.0.1', '-W', '-t', 'cursorBlink=true', '/bin/su', '-', ttydUser], {
       stdio: 'ignore',
       detached: true,
     });