It is best to start with the simplest option. When 2026 rolls around, it would be easiest for Moscow and Washington to continue to abide by the limits of the expiring treaty. The two sides should also negotiate to resume on-site inspections — Vladimir Putin himself will have to be convinced that it is in Russia’s national security interest to do so. Perhaps the strengthening of the US nuclear industrial complex can be brought to his attention in a way that makes Russia’s interest in implementing the treaty abundantly clear.
As for the Chinese, if they reach 1,500 warheads by 2035 and continually refuse to talk then the US and its allies must consider a build-up.
The worst-case scenario is that Russia and China are hell-bent on increasing their nuclear holdings at the cost of global stability. If that occurs, the US will be ready and able to respond.
What it’s always been, making the first strike more likely to achieve a certain amount of destruction when accounting for improvements in defence.