src/Pure/Tools/phabricator.scala

     def execute_raw(method: String, params: JSON.T = JSON.Object.empty): JSON.T = {
       Isabelle_System.with_tmp_file("params", "json") { params_file =>
         File.write(params_file, JSON.Format(JSON.Object("params" -> JSON.Format(params))))
         val result =
           Isabelle_System.bash(
-            "ssh -p " + ssh_port + " " + Bash.string(ssh_target) +
+            SSH.client_command(port = ssh_port) + " -- " + Bash.string(ssh_target) +
             " conduit " + Bash.string(method) + " < " + File.bash_path(params_file)).check
         JSON.parse(result.out, strict = false)
       }
     }