Payment Rails

What happens when the gap between payment intent and settlement finality collapses to zero?

The same Three Flows architecture governs how payments settle:

INTENT → ROUTE → INFRASTRUCTURE → SETTLE → FEEDBACK

The Shift

From	To
5-day correspondent hops	Sub-second finality
Hidden FX spreads (2-4%)	Transparent on-chain fees
Card networks as gatekeepers	Programmable settlement
Human-initiated transactions	Agent-initiated transactions
Monthly billing cycles	Real-time micropayments

Layer	Technology	Speed	Cost	Best For
Traditional	Correspondent banks	3-5 days	1-3%	Legacy B2B
Card networks	Visa, Mastercard	1-3 days	1-2%	Consumer checkout
Modern stablecoin	Ethereum	~12 min	$5-50	High-value, low-frequency
Fast stablecoin	Solana	~400ms	$0.01-0.25	Consumer, DeFi
Machine-tempo	Sui	~390ms + PTB batching	<$0.01	Agent commerce, DePIN

Three protocol families competing to become the default rails for agent transactions:

Protocol	Settlement	Who
ACP	Card rails via Stripe	OpenAI + Stripe
AP2	Multi-rail (card + stablecoin)	Google, with Sui as launch partner
x402	Stablecoin on-chain	Coinbase + Google + Ethereum Foundation

See Agent Commerce for the full standards war.

Provider	Role	Connection
Stripe	Payment processing, ACP co-author, Bridge acquisition	CEO on Meta board. Bridge received OCC national trust charter.
Coinbase	x402 protocol, Base L2, crypto on/off-ramp	Commerce SDK for agent-native payments
Shopify	UCP co-developer with Google	Merchant-side agent commerce

Payment rails operate across the full ABCD stack:

Layer	Function in Payments
AI	Route optimization, fraud detection, agent intent
Blockchain	Settlement, proof, immutable receipts
Crypto	Incentive alignment, tokenized coordination
DePIN	Physical infrastructure settlement (sensors, devices, energy)