Skip to main content
Fastx402 is an x402 payment facilitator that lets AI agents and applications pay for resources on Ethereum mainnet using USDC. It achieves sub-second settlement through FAST RPC preconfirmations.

​
The Problem

Ethereum’s 12+ second finality makes it unsuitable for real-time agent payments. An AI agent that needs to pay for an API call can’t wait 12 seconds for confirmation — it needs a response in milliseconds. Existing x402 facilitators solve this by operating on Base or Solana, but that means agents can’t access Ethereum’s deep USDC liquidity.

​
How It Works

Fastx402 uses USDC’s native EIP-3009 transferWithAuthorization function for gasless, signature-based payments:
  1. An agent encounters a 402 Payment Required response from a resource server.
  2. The agent signs an EIP-712 authorization message — no on-chain transaction needed.
  3. The resource server forwards the signed payment to Fastx402’s /settle endpoint.
  4. Fastx402 verifies the signature and submits the transaction via FAST RPC.
  5. FAST RPC preconfirms the transaction in ~100-200ms.
  6. The resource server receives confirmation and grants access.

​
Key Features

  • Sub-second settlement — ~1.2 seconds end-to-end via FAST RPC preconfirmations (vs 12+ seconds on standard Ethereum).
  • Zero gas for agents — Agents only need USDC. A relay wallet submits the on-chain transaction and covers gas.
  • Zero fees — No facilitator fee during the promotional period.
  • Mainnet liquidity — Access Ethereum’s largest stablecoin issuance and DeFi ecosystem directly.
  • x402 compatible — Drop-in replacement for any x402 facilitator. Works with the standard x402 flow.

​
Learn More

Fastx402 Developer Docs

Full API reference, EIP-3009 signing guide, and error codes.

What is FAST RPC?

The preconfirmation RPC that powers Fastx402 settlement.