HEAsoft 6.7 is now available. This includes XSPEC v12.5.1. The biggest change is in gain fitting which has been reworked as the preliminary step towards allowing the creation of response models. Response models will be created analogously to spectral models and will be used to either replace or augment response matrices.
This release is also the first which does not include XSPEC v11. This version has in practice not been supported for some time and it is getting increasingly difficult to ensure that it builds and runs on all systems.