Researchers have launched BLAZ4R, the first living catalog of confirmed blazars seen at redshifts over 4, offering a window into the first 2 billion years of cosmic history. This preprint (not yet peer-reviewed) from arXiv compiles 54 such objects using X-ray detections from the eROSITA instrument aboard the SRG spacecraft, combined with radio spectra, morphology, and multiwavelength data; the methodology focuses on confirming sources and characterizing their jet properties, with a sample size of 54. The team finds jetted sources appear more common than non-jetted ones at these high redshifts but show no major differences from the broader early universe active galaxy population. Limitations include the diverse properties that prevent clear identification of the exact fast-accretion processes needed to explain these early jetted black holes. Source: https://arxiv.org/abs/2603.24659