Hi Emo, In XML documentation of compiler: userthread should be usethread without r In API documentation of MjModel: "" int* exclude_signature;// (body1+1)<<16 + body2+1"" I think the formula should be ((body1+1)<<16) + body2+1 with explicit parenthesis. since in both new version C++ and Python, it will calculate the 16 + body2+1 first before bit operator. Same apply for contact include