A Join unioned its tools into the first target only, leaving other target bodies the tool overlapped or touched as separate, interpenetrating bodies. Each tool now merges with every target it meets (shared material or face contact, tested on the operands' boundaries) into one body under the first one's name; absorbed bodies are removed and their threads follow. A tool that meets no target still joins the first target as a separate lump. Sheet metal and mesh bodies are never absorbed. Co-Authored-By: Claude Opus 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01J53sR6gEaVt56soFDpTck8