Block swap keeps the frozen weights of the last N transformer blocks in system memory and lets ComfyUI's weight casting fetch them one layer at a time. The idea and the block count as the one knob follow musubi-tuner's block swap (kohya-ss, Apache License 2.0); this is an independent implementation. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01MpnF7GwNGMbngU11wjym7P