Updated bounds on the (1, 2) neutrino oscillation parameters after first JUNO results

Within the standard 3 ν framework, we discuss updated bounds on the leading oscillation parameters related to the ( ν 1 , ν 2 ) states, namely, the squared mass difference δ m 2 = m 2 2 − m 1 2 and the mixing parameter sin 2 θ 12 . A previous global analysis of 2024 oscillation data estimated δ m 2 and sin 2 θ 12 with fractional 1 σ errors of about 2.3% and 4.5%, respectively. First we update the analysis by applying the latest SNO+ (Sudbury Neutrino Observatory Plus) constraints that slightly shift the ( δ m 2 , sin 2 θ 12 ) best fits. Then we apply the constraints placed by the first Jiangmen Underground Neutrino Observatory results that significantly reduce the uncertainties of both parameters. Our updated global bounds (as of 2025) can be summarized in terms of a bivariate Gaussian as: δ m 2 / 10 − 5 eV 2 = 7.48 ± 0.10 and sin 2 θ 12 = 0.3085 ± 0.0073 (with error correlation ρ = − 0.20 ), corresponding to 1 σ uncertainties as small as 1.3% and 2.4%, respectively. We also comment on minor physical and statistical effects that, in the future, may contribute to lift the current mass-ordering degeneracy of ( δ m 2 , θ 12 ) estimates.