RAILS
x402, A2A, and the rails underneath the wallets
Payment-native HTTP and agent-to-agent messaging are converging. A map of which issuer supports what.
9 min ·
x402
The revived HTTP 402 pattern turns a paywalled response into a machine-payable one: the server quotes, the agent settles, the request replays. Coinbase ships it natively; others bridge to it.
Agent-to-agent messaging
A2A gives agents a way to negotiate before they transact. Payment and messaging converge at the point where a quote becomes an authorization, which is exactly where guardrails have to be evaluated.
Card rails still matter
Stripe's agent-authorized Link flow shows the incumbent path: existing card rails, new authorization semantics. For most commerce it will out-reach on-chain settlement for some time.