Supported networks

Identifiers and USDC contracts for the blockchains Facilitator Service supports

Blockchains

• Arc
• Base
• Polygon PoS

The upto scheme is available on all supported mainnet networks and Arc testnet.

Dynamic lookup

Facilitator Service exposes the current schemes and USDC contracts dynamically through /supported. Advertise upto in your payment requirements only on networks where /supported lists an upto kind.

Identifiers and contracts

Use the CAIP-2 value as the network field and the USDC contract as the asset field in your x402 paymentRequirements. The schemes column lists the x402 payment schemes Facilitator Service accepts on each blockchain.

Mainnet

Blockchain	CAIP-2	USDC contract	Schemes
Arc	eip155:5042	0x3600000000000000000000000000000000000000	exact, upto
Base	eip155:8453	0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913	exact, upto
Polygon PoS	eip155:137	0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359	exact, upto

Testnet

Blockchain	CAIP-2	USDC contract	Schemes
Arc	eip155:5042002	0x3600000000000000000000000000000000000000	exact, upto
Base Sepolia	eip155:84532	0x036CbD53842c5426634e7929541eC2318f3dCF7e	exact
Polygon PoS Amoy	eip155:80002	0x41E94Eb019C0762f9Bfcf9Fb1E58725BfB0e7582	exact

Usage-based payment contracts

upto payments use these contracts on every network that supports upto:

Contract	Address
Permit2	0x000000000022D473030F116dDEE9F6B43aC78BA3
x402 Permit2 proxy	0x4020A4f3b7b90ccA423B9fabCc0CE57C6C240002

Buyers approve Permit2 to spend their USDC, onchain or with a signed EIP-2612 permit. The proxy is the spender the buyer signs, and the contract Facilitator Service calls to settle.

Confirmation thresholds

Facilitator Service reports /settle and /status as completed only after the threshold for the target blockchain is met.

Blockchain	Threshold
Arc	Instant finality
Base	L2 block inclusion, canonical receipt, and USDC Transfer event verified
Polygon PoS	Standard Polygon PoS finality

On Base, a verified reorg after completion moves the payment to failed with reason=reorged. Facilitator Service never resubmits a reorged payment automatically.