Most premium cardholders lose $500–$1,000 a year not because they don't have good cards, but because managing Amex credits, Chase offers, and optimal card routing across dozens of merchants is genuinely hard to track. CardStack links to your real transaction data via Plaid and applies AI to surface what you're missing: which credits you haven't used, which Amex and Chase offers you're not enrolled in, and which card you should have swiped at your last purchase. It calculates your true ROI per card — not the theoretical value from a blog post, but based on how you actually spend. Auto-enrollment for eligible offers removes the manual work. Built specifically for Amex and Chase power users who know their cards have value but suspect they're not capturing all of it.