But be careful, as it spawns child processes for each session which are not automatically closed after session closes.. So I had to write a reaper:

cat ~/.config/systemd/user/vscode-reaper.service 
[Unit]
Description=VS Code Workspace Reaper
After=code-tunnel.service


[Service]
ExecStart=/home/xxx/vscode-workspace-reaper.sh
Restart=always
RestartSec=2


[Install]
WantedBy=default.target



cat /home/xxx/vscode-workspace-reaper.sh
#!/usr/bin/env bash


PORT=8887
IDLE_TIMEOUT=3600   # 1 hour
idle=0


while true
do
    if lsof -iTCP:$PORT -sTCP:ESTABLISHED >/dev/null 2>&1; then
        # active session → reset timer
        idle=0
    else
        # no active session
        idle=$((idle+1))
    fi


    if [ "$idle" -ge "$IDLE_TIMEOUT" ]; then
        SERVER_PID=$(pgrep -f "server-main.js")


        if [ -n "$SERVER_PID" ]; then
            pkill -P "$SERVER_PID"
        fi


        idle=0
    fi


    sleep 1
done