The cosmic infrared background (CIB) arises from the integrated emission of dusty, star-forming galaxies over cosmic time, and its angular fluctuations cross-correlate with galaxy surveys, weak lensing maps, and even the cosmic X-ray and microwave backgrounds (Kashlinsky et al. 2018; Maniyar et al. 2021). ΛCDM-based halo and star-formation models can broadly fit these cross-correlations but often require tuned bias, redshift distributions, and star-formation efficiencies, while unexplained excess large-scale CIB power and strong coherence with other backgrounds hint at additional or very early source populations that are difficult to reconcile with standard galaxy-formation histories (Cooray et al. 2012; Viero et al. 2013).