Stripe’s secondary-market valuations have climbed to the $180–184 billion range in recent months, outpacing American Express’s public market capitalization near $208 billion and supporting the 63% implied probability that Stripe finishes higher on December 31. Recent catalysts include the company’s $7.5–8 billion acquisition of OpenRouter to bolster AI model routing, expansion of stablecoin card programs toward 100 countries, a FedEx logistics partnership, and new agentic-commerce tools that position Stripe for faster growth in machine-driven payments. American Express maintains steady revenue from its premium card franchise but faces slower expansion in a mature payments sector. With only weeks remaining before year-end resolution, any further secondary repricing or Amex share-price volatility could shift the market-implied odds.