The observed cosmological constant may originate as the minimum value $U_{\min }$ of a scalar field potential, where the scalar field is frozen due to a large mass $m$. If this vacuum is metastable, it may decay to a true vacuum either at present or in the future. Assuming its decay rate $\mathrm{\Gamma }$ is comparable to the Hubble expansion rate $H_0$, we estimate the scale of true vacuum bubbles and analyze their evolution. We find that their initial formation scale is submillimeter, and their tension causes rapid collapse if $m\gtrsim 1.7\times {10}^{-3}\mathrm{eV}$. For smaller masses, the bubbles expand at the speed of light. We extend our analysis to scalar-tensor theories with nonminimal coupling, finding that the nucleation scale of gravitational constant bubbles remains consistent with the submillimeter regime of general relativity. The critical mass scale remains around ${10}^{-3}\mathrm{eV}$, similar to the minimally coupled case. A theoretical estimate at redshift $z_{\mathrm{obs}}\sim 0.01$ suggests an observable bubble radius of $\sim 50\mathrm{Mpc}$, implying a gravitational transition triggered $\sim 300\mathrm{Myr}$ ago, with a present-day size approaching 100 Mpc. Additionally, we explore mass ranges ($m<{10}^{-3}\mathrm{eV}$) and coupling parameter $\xi$ ranges (${10}^{-8}{\mathrm{eV}}^{2-n}$ to ${10}^{-1}{\mathrm{eV}}^{2-n}$) that lead to a variation in the gravitational constant $\mathrm{\Delta }G/G_N$ within the 1%–7% range. This analysis is conducted in the framework of nonminimal coupling theories, where the coupling function takes the form $F(\varphi )=1/\kappa -\xi {\varphi }^n$, with $\kappa =8\pi G_N$ and $2\le n\le 9$. Finally, we review various local physics or/and transition based proposed solutions to the Hubble tension, including ultralate-time transitional models ($z\sim 0.01$), screened fifth-force mechanisms, and the ${\mathrm{\Lambda }}_{\mathrm{s}}\mathrm{CDM}$ model, which features a transition at $z\sim 2$. We discuss observational hints supporting these scenarios and the theoretical challenges they face.

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• Alternative gravity theories
• Cosmology
• Dark energy
• Evolution of the Universe
• General relativity
• Large scale structure of the Universe