The Standard Model electroweak vacuum is metastable rather than absolutely stable.

The verdict rests on three legs, unchanged in status from the previous pass but with the conditionality now explicitly quantified.

First, the supporting computation: next-to-next-to-leading-order analyses of the Higgs effective potential (Degrassi et al. 2012; Buttazzo et al. 2013; Bednyakov et al. 2015; Steudtner et al., Phys. Rev. D 110, 115017, 2024) consistently find the quartic coupling turning negative near 10^10 to 10^11 GeV for central parameters. The subclaim recording this is robust and not seriously disputed for the stated inputs; the inference from a negative quartic to a deeper minimum and hence metastability is sound.

Second, the counter-consideration, that top-quark mass uncertainties leave absolute stability consistent with current measurements, stands supported: the cross-section pole-mass extraction (172.4 ± 0.7 GeV) sits within about 1.9 sigma of the ~171 GeV stability boundary, and the apparent five-sigma exclusion from direct measurements depends on the contested identification of the Monte Carlo mass with the pole mass. This is what keeps the status at supported rather than verified.

Third, the presupposition that no new physics modifies the Standard Model below the instability scale has now been assessed for the first time: unknown, with credence 0.35 that it holds. Collider null results cover only up to roughly 10^4 GeV of the roughly 10^10 GeV range the extrapolation spans, and established Standard Model gaps (neutrino masses, dark matter) make intervening Higgs-coupled new physics a live possibility. This does not weaken the computation or change the status, because the claim is read, as before, as a statement about the Standard Model's own potential; but the conditional framing is now the leading qualification rather than a closing caveat. Read instead as a claim about the actual vacuum of nature, the credence would be substantially lower, roughly the product of the in-model credence and the probability that the extrapolation is licensed.

Credence 0.8 applies to the in-model reading and reflects the two-to-three sigma preference for metastability over stability at central parameter values, tempered by the Monte Carlo mass ambiguity. What would change the conclusion: a downward shift of order 1 GeV in the top pole mass or an upward shift in the strong coupling would flip the verdict toward stability; a firm demonstration that the Monte Carlo mass tracks the pole mass to within a few hundred MeV would harden it toward verified; discovery of new physics coupling to the Higgs below the instability scale would not falsify the in-model claim but would sharply reduce its relevance to the actual vacuum. No source instances are attached; the assessment rests on the primary literature.