Visa+Stablecoin Card Payment — Retail Payments

L5 APPLICATIONCARD

L4 ACCOUNTCARD

Step 1 · Cardholder WalletPolicy-Enforced

"The customer taps their card — the payment begins on traditional card rails."

Cardholder initiates payment via Visa contactless tap. L4 Account (card credential, tokenized PAN) and L5 Application (Apple Pay / wallet UX) are lit. The payment begins in the traditional card network before crossing into stablecoin settlement.

Counterparty: Cardholder's issuing bank
Latency: Instant · NFC tap
Finality: Authorization only — not yet settled
Vendors: Coinbase Wallet · Coinbase Smart Wallet (ERC-4337 account abstraction — passkey-based onboarding) · EOA + ERC-4337 Smart Account (Coinbase Smart Wallet is the canonical Coinbase-operated AA surface) · Coinbase Custody Trust Company, LLC (New York limited-purpose trust company under NYDFS) · Coinbase Prime brokerage (institutional custody + execution surface) · third-party qualified custodians per integrator (Anchorage · BitGo · Fireblocks) · Securitize LLC (SEC-registered transfer agent; runs Reg D 506(c)(2)(ii) accredited-investor verification workflow; transfer-agent function is off-chain, identical on Base and Ethereum) · Coinbase Paymaster (gas-sponsorship primitive for Coinbase Smart Wallet flows · ERC-4337 paymaster contract) · Coinbase Verifications (Ethereum Attestation Service-backed attestation product binding Coinbase-verified identity attributes — country of residence, accredited-investor status, etc. — to addresses) · Securitize Markets ATS (SEC-registered ATS) · BlackRock BUIDL · other Securitize-issued RWAs (Base deployments via multichain expansion — ACRED was Ethereum-mainnet and Base availability is NOT independently confirmed)
Chain: Base (Coinbase (sole sequencer operator at launch; decentralization on roadmap))

L4 ACCOUNTREGULATED (cross-boundary)

L3 EXECUTIONREGULATED (cross-boundary)

Step 2 · Card → USDC InterchangePolicy-Enforced

"The correspondent bank handoff — value crosses from the card network's authorization rail to the stablecoin settlement rail."

The asymmetric interchange: value transitions from Visa's card-authorization rail to USDC settlement on Base. L3 Execution (interchange logic) and L4 Account (balance conversion) are lit. The dot-fill encoding is asymmetric — hollow (stablecoin) / filled (regulated card) — reflecting the regulatory weight difference between the two rails.

Counterparty: Visa network + Coinbase settlement
Latency: ~5s · interchange processing
Finality: Interchange confirmed — settlement pending
Vendors: Uniswap v4 · Aerodrome (Base-native AMM derived from Velodrome) · BaseSwap · Chainalysis OFAC Oracle (on-chain SDN-list enforcement primitive · code-enforced at the contract layer for opt-in callers) · Circle CCTP v2 (canonical USDC burn-and-mint cross-chain transport between Base and Ethereum / other CCTP-supported chains) · Base Bridge (OP Stack canonical L1 ↔ L2 bridge with 7-day challenge window · L1-escape-hatch via force-inclusion) · Securitize DS Protocol (on-chain transfer-restriction smart-contract framework enforcing eligible-investor whitelisting — ACRED is Ethereum-only; BUIDL multi-chain expansion to Base reported in public reporting but primary-source confirmation pending) · EOA + ERC-4337 Smart Account (Coinbase Smart Wallet is the canonical Coinbase-operated AA surface) · Coinbase Custody Trust Company, LLC (New York limited-purpose trust company under NYDFS) · Coinbase Prime brokerage (institutional custody + execution surface) · third-party qualified custodians per integrator (Anchorage · BitGo · Fireblocks) · Securitize LLC (SEC-registered transfer agent; runs Reg D 506(c)(2)(ii) accredited-investor verification workflow; transfer-agent function is off-chain, identical on Base and Ethereum)
Chain: Base (Coinbase (sole sequencer operator at launch; decentralization on roadmap))

L5 APPLICATIONWALLET

L4 ACCOUNTWALLET

◆ Enforcement Line — code-enforced at this layer

Step 3 · Merchant Wallet (Base)Code-Enforced

"The merchant receives stablecoin settlement — faster and cheaper than waiting for card-network batch settlement."

USDC arrives at the merchant's wallet on Base. The card payment has been settled in stablecoins: the merchant receives value in ~5 seconds instead of the card network's T+1 or T+2 batch cycle. L4 Account and L5 Application lit.

Counterparty: Merchant wallet on Base
Latency: ~2s · single Base block after interchange
Finality: Final on Base block confirmation
Vendors: Coinbase Wallet · Coinbase Smart Wallet (ERC-4337 account abstraction — passkey-based onboarding) · EOA + ERC-4337 Smart Account (Coinbase Smart Wallet is the canonical Coinbase-operated AA surface) · Coinbase Custody Trust Company, LLC (New York limited-purpose trust company under NYDFS) · Coinbase Prime brokerage (institutional custody + execution surface) · third-party qualified custodians per integrator (Anchorage · BitGo · Fireblocks) · Securitize LLC (SEC-registered transfer agent; runs Reg D 506(c)(2)(ii) accredited-investor verification workflow; transfer-agent function is off-chain, identical on Base and Ethereum) · Coinbase Paymaster (gas-sponsorship primitive for Coinbase Smart Wallet flows · ERC-4337 paymaster contract) · Coinbase Verifications (Ethereum Attestation Service-backed attestation product binding Coinbase-verified identity attributes — country of residence, accredited-investor status, etc. — to addresses) · Securitize Markets ATS (SEC-registered ATS) · BlackRock BUIDL · other Securitize-issued RWAs (Base deployments via multichain expansion — ACRED was Ethereum-mainnet and Base availability is NOT independently confirmed)
Chain: Base (Coinbase (sole sequencer operator at launch; decentralization on roadmap))

Step 1 · Cardholder WalletPolicy-Enforced

Step 2 · Card → USDC InterchangePolicy-Enforced

Step 3 · Merchant Wallet (Base)Code-Enforced

Other Retail Payments Paths