    if (!is_present_hf("X-VICIdial-Client-Id")) {
        xlog("L_WARN", "INVITE received without X-VICIdial-Client-Id header\n");
        t_reply("400", "Bad Request - Missing Client ID");
        exit;
    }

    if ($rU == $null) {
        xlog("L_WARN", "INVITE received with empty Request-URI username\n");
        t_reply("400", "Bad Request - Missing User");
        exit;
    }

    $var(full_client_id) = $hdr(X-VICIdial-Client-Id);
    # Extract parent ID
    if ($var(full_client_id) =~ "^(CID_[0-9]+)-[a-z]$") {
        $var(parent_client_id) = $(var(full_client_id){re.subst,/^(CID_[0-9]+)-[a-z]$/\1/});
    } else {
        $var(parent_client_id) = $var(full_client_id);
    }

    # CPS Check and Rate Limiting
    lock("cps_counter");

    # Get current CPS count and max limit
    $var(current_cps) = $sht(client_limits=>$var(parent_client_id));
    $var(max_cps) = $sht(client_max_cps=>$var(parent_client_id));

    xlog("L_INFO", "CPS Check - Client: $var(parent_client_id), Current: $var(current_cps), Max: $var(max_cps)\n");

    # Check for configured limit
    if($var(max_cps) == $null) {
        unlock("cps_counter");
        xlog("L_WARN", "No CPS limit configured for client $var(parent_client_id)\n");
        t_reply("403", "Client Not Authorized");
        exit;
    }

    # Get concurrent calls
    $var(concurrent_calls) = $sht(client_calls=>$var(parent_client_id));
    if($var(concurrent_calls) == $null) {
        $var(concurrent_calls) = 0;
    }

    # Strict limit check
    if($var(concurrent_calls) >= $var(max_cps)) {
        unlock("cps_counter");
        xlog("L_WARN", "Concurrent call limit reached for $var(parent_client_id): $var(concurrent_calls)/$var(max_cps)\n");
        t_reply("503", "Concurrent Call Limit Exceeded");
        exit;
    }

    # Allow call and increment counter
    if($var(current_cps) == $null) {
        $sht(client_limits=>$var(parent_client_id)) = 1;
    } else {
        $sht(client_limits=>$var(parent_client_id)) = $var(current_cps) + 1;
    }

    xlog("L_INFO", "Call allowed for $var(parent_client_id): Concurrent=$var(concurrent_calls+1)/$var(max_cps)\n");
    unlock("cps_counter");

    $var(user) = $rU;    

    # Extract parent client ID if this is a child ID
    if ($var(full_client_id) =~ "^(CID_[0-9]+)-[a-z]$") {
        $var(parent_client_id) = $(var(full_client_id){re.subst,/^(CID_[0-9]+)-[a-z]$/\1/});
        $var(is_child) = 1;
    } else {
        $var(parent_client_id) = $var(full_client_id);
        $var(is_child) = 0;
    }

    $avp(full_client_id) = $var(full_client_id);
    $avp(parent_client_id) = $var(parent_client_id);
    $avp(user) = $var(user);
    $var(call_id) = $ci;

    route(GENERATE_SERIAL_NUMBER);
    
    # Track client calls
    lock("client_counter");
    
    # Update parent counter
    $var(parent_calls) = $sht(client_calls=>$var(parent_client_id));
    if($var(parent_calls) == $null) {
        $var(parent_calls) = 0;
    }
    $sht(client_calls=>$var(parent_client_id)) = $var(parent_calls) + 1;
    
    # If it's a child ID, update its individual counter too
    if ($var(is_child) == 1) {
        $var(child_calls) = $sht(client_calls=>$var(full_client_id));
        if($var(child_calls) == $null) {
            $var(child_calls) = 0;
        }
        $sht(client_calls=>$var(full_client_id)) = $var(child_calls) + 1;
    }
    
    # Store mappings
    $sht(client_calls=>$var(call_id)) = $var(parent_client_id);
    $sht(client_original=>$var(call_id)) = $var(full_client_id);
    unlock("client_counter");

    # Find destination with lowest active calls
    $var(min_calls) = 999;
    $var(selected_dst) = "";
    
    lock("calls_counter");
    
    if (ds_select_dst("4", "4")) {
        $var(count) = 0;  # Add counter
        $var(current_calls) = $sht(active_calls=>$du);
        if ($var(current_calls) == $null) {
            $var(current_calls) = 0;
        }
        
        if ($var(current_calls) < $var(min_calls)) {
            $var(min_calls) = $var(current_calls);
            $var(selected_dst) = $du;
        }

        while(ds_next_dst() && $var(count) < 350) {  # Set higher than 280
            $var(count) = $var(count) + 1;
            $var(current_calls) = $sht(active_calls=>$du);
            if ($var(current_calls) == $null) {
                $var(current_calls) = 0;
            }
            
            if ($var(current_calls) < $var(min_calls)) {
                $var(min_calls) = $var(current_calls);
                $var(selected_dst) = $du;
            }
        }
    }
    
    if ($var(selected_dst) != "" && $var(min_calls) < 25) {
        $du = $var(selected_dst);
        # Add this block - Double check the count hasn't changed
        $var(current_count) = $sht(active_calls=>$du);
        if ($var(current_count) >= 25) {
            unlock("calls_counter");
            xlog("L_ERROR", "Count increased during selection for $du to $var(current_count)\n");
            t_reply("503", "Service Unavailable");
            exit;
        }
        # Store Call-ID to destination mapping
        $sht(active_calls=>$var(call_id)) = $du;
        # Increment call counter
        $sht(active_calls=>$du) = $var(min_calls) + 1;
        unlock("calls_counter");
        route(RELAY_INVITE);
    } else {
        unlock("calls_counter");
        xlog("L_NOTICE", "Unlocked $ci");
        $du = "sip:34.125.5.64:5060";
        t_on_failure("FINAL_FAILURE");
        if (!t_relay()) {
            t_reply("500", "Internal Server Error");
        }
    }
} else {
    route(RELAY);
}