Recently, there has been considerable debate regarding potential evidence for the dynamical nature of dark energy, particularly in light of baryon acoustic oscillation measurements released by the Dark Energy Spectroscopic Instrument (DESI) survey. In this work, we propose an agnostic test that simultaneously constrains the dark energy equation of state and probes the possibility of a transition between the quintessence and phantom regimes, or vice versa. Our initial approach is independent of physical priors, allowing the data to determine which behavior best fits the parameters. We then consider a minimally modified gravity theory known as VCDM, into which we can map our initial approximation, placing it within a theoretically stable framework. To this end, we incorporate the most up-to-date data sets available, including baryon acoustic oscillation measurements from DESI-DR2, type Ia supernovae from the PantheonPlus, DESY5, and Union3 samples, and cosmic microwave background data from Planck. Our analysis reveals strong and statistically significant evidence for a quintessence-phantom transition across various data combinations. The strongest evidence is found for Planck$+\mathrm{DESI}+\mathrm{DESY}5$, with a significance exceeding $\sim 5\sigma$ in favor of a quintessence-phantom transition at $z_{†}=0.493_{-0.081}^{+0.063}$. Beyond this redshift, the equation of state remains within the phantom regime, while for $z<z_{†}$, it favors the quintessence regime. Despite this strong indication, we find that such transitions do not resolve the $H_0$ tension.

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• Alternative gravity theories
• Cosmological parameters
• Dark energy