doi:10.1088/1475-7516/2026/03/023engCarmona, J.M.Cortés, J.L.Reyes, M.A.Superluminal constraints from ultra-high-energy neutrino eventsART-2026-149414The 220+570-100 PeV neutrino detected by KM3NeT marks the beginning of ultrahigh-energy neutrino astronomy and provides a powerful probe of Lorentz Invariance Violation (LIV). In superluminal scenarios, neutrinos can decay through vacuum e-e+ pair emission or neutrino splitting. Previous analyses of the KM3-230213A event relied on simplified survival-probability estimates and, in some cases, used inaccurate decay-width expressions or neglected redshift and threshold effects. In this work we present a unified and self-consistent framework that corrects these issues and applies to both the energy-independent (n = 0) and quadratic (n = 2) superluminal cases. We collect and recast the decay-width and threshold expressions, clarify their flavor dependence, and include a consistent treatment of cosmological propagation. We also assess the impact of cascade regeneration and show that cascade effects are negligible for the purpose of setting LIV bounds. The survival-probability approximation adopted in previous works is therefore justified, while our framework provides a coherent basis for future analyses of superluminal neutrino constraints, which should consistently include possible time-delay signatures.2026http://zaguan.unizar.es/record/17166310.1088/1475-7516/2026/03/023http://zaguan.unizar.es/record/171663oai:zaguan.unizar.es:171663info:eu-repo/grantAgreement/ES/DGA/E21-23Rinfo:eu-repo/grantAgreement/ES/MICINN/PGC2022-126078NB-C21info:eu-repo/grantAgreement/ES/MICINN/PID2024-160228NB-I00Journal of Cosmology and Astroparticle Physics 2026, 03 (2026), 023All rights reservedhttp://www.europeana.eu/rights/rr-f/info:eu-repo/semantics/closedAccess