Traders assign a 96.4% probability to no US ally acquiring nuclear weapons before 2027 because technical, legal, and political barriers make rapid weaponization highly unlikely within the narrow timeframe. US civil nuclear cooperation agreements with South Korea and Saudi Arabia, finalized in 2025–2026, permit limited uranium enrichment for civilian or naval purposes but maintain strict caps below weapons-grade levels, require congressional oversight, and align with nonproliferation standards that extend breakout timelines well into the 2030s. South Korea’s nuclear-powered submarine program targets initial vessels only in the mid-to-late 2030s, while Saudi enrichment pathways under the July 2026 deal remain at early civilian stages without declared weapons intent. Allies continue to prioritize US extended deterrence and alliance frameworks over independent arsenals, with public and elite opinion in Japan and Europe showing limited support for proliferation despite regional tensions. Late shifts could occur through undisclosed enrichment advances, sudden policy reversals amid acute threats, or verified secret programs, though such developments would still face formidable verification and production hurdles before 2027.