GUNDAM was born as a fork of the xsllhFitter project which was developped and used by the cross-section working group of T2K. The original project can be found on gitlab: https://gitlab.com/cuddandr/xsLLhFitter.

GUNDAM has originally been developed as an new fitter to perform T2K oscillation analysis, and provide an expandable base on which future studies with the Upgraded ND280 Detectors will be performed.