Modern Treasury's Stablecoin Sandwich

Modern Treasury, after acquiring stablecoin startup Beam, is launching an integrated PSP that unifies fiat and stablecoin payments under a single API. The core concept is the 'Stablecoin Sandwich': fiat enters on one side, gets converted to stablecoins for cross-border transfer, then converted back to fiat on the other end — making crypto rails invisible to end users. This approach lets companies experiment with stablecoins without building separate integrations, using the same endpoints as ACH, FedNow, and Wire. The key trade-off: stablecoins are faster and cheaper than traditional rails but are unforgiving — transactions are irreversible, requiring correctness upfront. The strategy mirrors Stripe's evolution toward a unified payment abstraction, applied now to bridging fiat and crypto.