Morgan Stanley's commanding 81.5% implied probability in the Polymarket contract stems primarily from its designation as the prospective lead-left bookrunner for Anthropic's anticipated IPO, reinforced by its leadership of the company's $15 billion pre-IPO revolving credit facility finalized in September 2026. This structure mirrors precedents like SpaceX and positions the bank to handle valuation discussions, investor allocations, and roadshow coordination ahead of a targeted mid-November listing. Goldman Sachs, at 16.4%, retains a secondary role as stabilization agent alongside JPMorgan and Citigroup, while smaller banks trail due to limited prior financing commitments. Recent investor-day outreach on October 14 and ongoing SEC review of the confidential S-1 filing further solidify the current hierarchy among the underwriting syndicate.