International diplomatic pressure and IAEA monitoring remain the primary drivers behind traders' 95.5% implied probability against an Iranian nuclear test before 2027. The UN nuclear watchdog's board referred Iran's nuclear dossier to the Security Council in September 2026—the first such action in two decades—highlighting unresolved safeguards issues and construction at underground sites without any confirmed detonation. Ongoing negotiations, sanctions regimes, and verification mechanisms have historically constrained testing despite enrichment advances, reflecting trader consensus shaped by verifiable restraint and institutional oversight. Realistic shifts could still arise from abrupt policy reversals, undetected breakout attempts, or major regional escalations that alter Iran's cost-benefit calculations within the remaining timeline.