x402 is instant and final. Castor is the dam: sellers bond USDC, and when a paid call leaks, the bond pays your agent back in seconds.
You’re the seller. Drag to stack logs into your bond, then throw a leaky call at it and watch who pays.
Payment settles before the response arrives. When the API hangs, crashes or answers with junk, the agent has already paid. Nobody pays it back. Castor is the refund button.
Castor never holds the agent’s money. The seller’s bond is the guarantee, so small calls stay as fast as plain x402.
API sellers lock a USDC bond in the Castor program. A bigger dam means bigger coverage and a better Beaver Score.
Plain x402 in USDC. It settles to the seller instantly. No escrow lock, no waiting, no new wallet.
Watchers see the response first-hand. Timeout, error or junk triggers a refund straight from the seller’s bond.
Only things a machine can prove. Nobody can fake a refund, and nobody can dodge one.
Middleware for x402 sellers, a wrapper for agent clients. Your stack stays the same; the river stops leaking.
Read the docs →1 import { castor } from "@castor/seller"; 2 3 app.use("/api/weather", castor.protect({ 4 price: "0.01 USDC", 5 checks: ["timeout:3s", "status", "schema"], 6 }));
1 import { withCastor } from "@castor/agent"; 2 3 const pay = withCastor(x402Client, { onlyProtected: true }); 4 const res = await pay.fetch("https://api.example.com/weather"); 5 // leaked? the refund lands in your wallet.
Bonds are USDC, so protection never depends on a chart. $CSTR is how the colony runs.
The token that runs the colony. The contract address drops on X first. Anywhere else is a fake.
Get the CA first →Watchers in the payment path see the response first-hand. Only provable checks count: timeout, error status, schema mismatch and empty payload. From Phase 02, staked watchers co-sign and get slashed for false reports.
No. The agent pays with plain x402 and the seller is paid instantly. The bond is the guarantee, so nothing sits in escrow for small calls.
Coverage is capped by bond size. When the dam is empty the seller loses the badge until it is topped up, and the $CSTR backstop pool covers what is left.
No. Refunds follow what watchers observed, never what the agent claims. A good answer never refunds.
Staking for watchers, arbiters, the backstop pool and vouching; fee discounts and catalog boosts for sellers; higher coverage for agents; governance; and buybacks from protocol fees.