Pagaya scores $500M, Upstart locks $1.5B, and Interactive Brokers proves consistency is the real fintech superpower. In today’s Fintech Stacks Daily, we break down how Castlelake became the go-to funding source for AI lenders, why Pagaya’s diving into auto loans, and how IBKR just delivered another stealth earnings win. Expect some shade, some stats, and a lot of fintech flavor.