Stringent constraint on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>C</mml:mi><mml:mi>P</mml:mi><mml:mi>T</mml:mi></mml:math> violation with the synergy of T2K-II, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>NO</mml:mi><mml:mi>ν</mml:mi><mml:mi mathvariant="normal">A</mml:mi></mml:math> extension, and JUNO

Neutrino oscillation experiments have measured precisely at few percent levels the mass-squared differences ($\mathrm{\ensuremath{\Delta}}{m}_{21}^{2}$, $\mathrm{\ensuremath{\Delta}}{m}_{31}^{2}$) of three neutrino mass eigenstates, and leptonic mixing angles (${\ensuremath{\theta}}_{12}$, ${\ensuremath{\theta}}_{13}$, ${\ensuremath{\theta}}_{23}$) by utilizing both antineutrino oscillations. The possible $CPT$ violation may manifest itself in difference parameters, making these promising tools for testing invariance unprecedented precision. We investigate empirically sensitivity test via splittings ($\mathrm{\ensuremath{\Delta}}{m}_{31}^{2}\ensuremath{-}\mathrm{\ensuremath{\Delta}}{\overline{m}}_{31}^{2}$) (${\mathrm{sin}}^{2}{\ensuremath{\theta}}_{23}\ensuremath{-}{\mathrm{sin}}^{2}{\overline{\ensuremath{\theta}}}_{23}$) with synergy T2K-II, $\mathrm{NO}\ensuremath{\nu}\mathrm{A}$ extension, JUNO experiments. If symmetry is found to be conserved, joint analysis will able establish limits $|\mathrm{\ensuremath{\Delta}}{m}_{31}^{2}\ensuremath{-}\mathrm{\ensuremath{\Delta}}{\overline{m}}_{31}^{2}|&lt;5.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\text{ }\text{ }{\mathrm{eV}}^{2}$ $|{\mathrm{sin}}^{2}{\ensuremath{\theta}}_{23}\ensuremath{-}{\mathrm{sin}}^{2}{\overline{\ensuremath{\theta}}}_{23}|&lt;0.10$ $3\ensuremath{\sigma}$ confidence level (CL) on violation, extending substantially current bound parameters. find that ($\mathrm{\ensuremath{\Delta}}{m}_{31}^{2}\ensuremath{-}\mathrm{\ensuremath{\Delta}}{\overline{m}}_{31}^{2}$), dependence statistical significance relevant parameters exclude conservation marginal, that, if best-fit values $\mathrm{\ensuremath{\Delta}}{m}_{31}^{2}$ $\mathrm{\ensuremath{\Delta}}{\overline{m}}_{31}^{2}$ $\mathrm{MINOS}(+)$ persists as true, combined rule out $4\ensuremath{\sigma}$ CL. With (${\mathrm{sin}}^{2}{\ensuremath{\theta}}_{23}\ensuremath{-}{\mathrm{sin}}^{2}{\overline{\ensuremath{\theta}}}_{23}$), depends strongly true value ${\ensuremath{\theta}}_{23}({\overline{\ensuremath{\theta}}}_{23})$ angle. In case maximal ${\ensuremath{\theta}}_{23}$, indicated T2K measurements, excluded CL or higher ${\ensuremath{\theta}}_{23}$ ${\overline{\ensuremath{\theta}}}_{23}$ remains true.