Python Computational Suite for Emergent Flatness and Dynamical Expansion in Environmental Transition Cosmology

etc-cosmo-core is an open-source Python library implementing the numerical solutions of Environmental Transition Cosmology (ETC). It provides full solver routines for background FLRW expansion under emergent Euclidean flatness ($k=0$), exact dynamical elimination of the cosmological constant ($\Lambda \equiv 0$), resolution of the Hubble (H0H_0H0) and growth (S8S_8S8) tensions, and galactic rotation curve evaluations without cold dark matter halos.