Paying with x402
x402 is an open protocol that lets machines pay machines, built around the HTTP 402 Payment Required status code that went largely unused for years. Cyphron supports it natively. An agent account can therefore pay for API calls, compute and services without a card, without an OAuth flow, and without a prepaid balance that needs refilling. Payments happen as fast as an HTTP request and response.
Robinhood Chain was built with this audience in mind: its stated purpose is to let agents trade, swap and pay. x402 is the natural way to express payments there. Services get a standard format for quoting a price, and agents get a standard format for paying it, inline, within the request they were already sending.
How a payment flows
Agent asks an x402-enabled service for a resource
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Service replies: 402 Payment Required
Headers specify amount, asset, recipient
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Agent's Cyphron wallet checks the request against its spend policy
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Within policy: agent signs and sends a confidential USDG transfer
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Agent sends the request again, this time with proof of payment
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Service verifies on-chain and returns the resource
No human is involved at any point, unless the amount exceeds the approval threshold set in the agent's spend policy. Transactions run at machine speed while your safeguards stay in place.
Payment patterns
- Pay-per-call: the most common pattern, where each request includes its own micropayment.
- Metered: the service charges in increments as usage builds up, rather than collecting in advance.
- Recurring: an x402 charge on a regular schedule, checked against the spend policy each time it comes due.
Why these payments are encrypted
x402 is inherently high volume, and an active agent can settle a large number of small payments every minute. If that stream were public, anyone interested could read your usage pattern and cost structure from it, which amounts to giving competitors free intelligence. Cyphron's confidential token contracts apply the same amount hiding to these payments (whether USDG, bridged USDC or ETH) as to every other transfer. Agents can transact without leaking telemetry.
Enabling x402
There is no switch to flip. Every Agent account has x402 active out of the box. All you need is a spend policy that allows the recipients you expect to pay. To set that up from code, see Agent and Policy Endpoints.