• File path: UnrankedServer\boiii\scripts\zm\gametypes\_clientids.gsc
• Compiler: https://github.com/shiversoftdev/t7-compiler or https://github.com/xensik/gsc-tool
• Empty default _clientids.gsc:

#include scripts\shared\system_shared;
#include scripts\shared\callbacks_shared;
#include scripts\shared\hud_util_shared;
#include scripts\shared\flag_shared;
#include scripts\shared\ai\zombie_utility;
#include scripts\zm\_zm_utility;

#namespace ezz_empty;


autoexec __init__sytem__()
{
    system::register("ezz_empty", ::__init__, undefined, undefined);
}
	
__init__()
{
	callback::on_start_gametype( ::init );
	callback::on_connect( ::on_player_connect );
}

init()
{
    level.clientid = 0;
}

on_player_connect()
{
    self.clientid = matchrecordnewplayer(self);
	if(!isdefined(self.clientid) || self.clientid == -1)
	{
		self.clientid = level.clientid;
		level.clientid++;
	}
}