Rocket Lab’s Neutron medium-lift rocket remains in active development with first-stage tank production aligned to a potential Q4 2026 pad delivery, yet recent SEC filings explicitly note that the window for an end-of-2026 debut is narrowing amid pending qualification testing, static fires, and integration milestones. Traders assign a 91% probability against a launch by December 31 because the vehicle’s Archimedes engines, carbon-composite structures, and reusable booster systems still require extensive ground testing before flight, consistent with prior schedule slips that prioritized operational reliability over speed. While rapid test success or accelerated manufacturing could theoretically enable a late-year attempt, the company’s emphasis on entering service ready for high-cadence operations makes any 2026 flight appear increasingly unlikely.