Steam writes localconfig.vdf via atomic rename (write temp + rename over original). chmod 444 on the file is bypassed by the rename. chmod 555 on the directory blocks rename-into, preserving the launch option across Steam restarts. Also unlocks the directory at the start of step 6 so re-running the script can update the launch option. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01D8ckUJQtj1pH8jtAddBDZs