Anthropic's active preparations for a November 2026 IPO, including recent prospectus details and a targeted marketing window around mid-month, drive the 96.5% market-implied odds it will list before OpenAI. CEO Sam Altman's September statements explicitly ruled out a 2026 debut for OpenAI, citing the need to address AI safety and alignment priorities amid rapid model advances like GPT-6, while the company pursues a private bridge round instead. This timeline contrast aligns with both firms' confidential SEC filings earlier in 2026 and Anthropic's revenue trajectory exceeding $65 billion annualized. Realistic shifts could still arise from Anthropic facing extended regulatory scrutiny, market volatility delaying its roadshow, or OpenAI accelerating if safety benchmarks are met sooner than anticipated, though current commitments make such reversals unlikely.