Psi–Continuum State–Space Diagnostics: Macroscopic diagnostics for late–time cosmic expansion

Psi–Continuum State–Space Diagnostics is an open-source Python software package providing the reference implementation of the macroscopic state–space diagnostic framework introduced in Psi–Continuum Cosmology v5. The package constructs a single macroscopic state–space coordinate, Ψ(z), directly from background expansion histories relative to the ΛCDM model, without introducing new physical fields or modifying gravity. Independent observational datasets are mapped onto smooth trajectories in state space, enabling a unified, model-independent comparison of late-time cosmological expansion histories. The software is purely diagnostic and operates at the background level. It is designed for reproducible analysis, visualization, and consistency checks of cosmological expansion data, including H(z) measurements and related datasets. The ΛCDM expansion history emerges naturally as the instantaneous-response limit of the macroscopic description. This software accompanies the preprint: Psi–Continuum Cosmology v5: A Macroscopic State–Space Response Framework for Late–Time Cosmic Expansion Zenodo DOI: https://doi.org/10.5281/zenodo.18088720