One morning in late 2025, I watched a card program's approval rate go to zero. Not at one merchant. At every merchant, everywhere, for about seventy minutes.

I was running fraud at the issuer. This is what happened, what it looked like from the merchant side, and the five things I now believe every merchant's decline monitoring should do because of mornings like that one.

Details below are anonymized and numbers are rounded. The mechanics are exactly as they happened.

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