X402 Networks and Payment Methods

Ace Data Cloud X402 currently settles around USDC and supports two types of chains: EVM and Solana. Different networks have different signing methods, asset addresses, gas behavior, and applicable scenarios, so you need to choose the network before integration.

¶ Network Identifiers Use CAIP-2

The accepts[].network of x402 v2 is a CAIP-2 identifier, not abbreviations such as base or skale. Clients must compare networks by CAIP-2 strings:

Network	CAIP-2 Identifier
Base	eip155:8453
SKALE Base	eip155:1187947933
Solana mainnet	solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp

¶ Support Matrix

Network	scheme	Asset	Signing Method	Applicable Scenario
Base	exact	Base USDC	EIP-3009 TransferWithAuthorization	Recommended by default, with mature wallet and liquidity support.
Base	upto	Base USDC + Permit2	Permit2 PermitWitnessTransferFrom	Post-metering APIs such as chat and models.
SKALE	exact	SKALE bridged USDC	EIP-3009 TransferWithAuthorization	Low gas costs, suitable for EVM payment verification and low-cost calls.
Solana	exact	Solana USDC	SPL TransferChecked	Solana wallets, Agents, or on-chain application scenarios.

upto is currently available only on Base. Actual available items are subject to the accepts returned by the API. You can also check the Facilitator:

curl https://facilitator.acedata.cloud/supported

The response from Facilitator /supported:

{
  "kinds": [
    { "x402Version": 2, "scheme": "exact", "network": "eip155:8453" },
    {
      "x402Version": 2,
      "scheme": "upto",
      "network": "eip155:8453",
      "extra": { "facilitatorAddress": "0xd019238EAA8a9Ca13C5792Ca10B4029D6ce25708" }
    },
    { "x402Version": 2, "scheme": "exact", "network": "eip155:1187947933" },
    {
      "x402Version": 2,
      "scheme": "exact",
      "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
      "extra": { "feePayer": "3SPm6qbgsDkj24MuR8Ss4sH97fziqyCiqFKDyeVU2igq" }
    }
  ]
}

Result description:

• The exact of Base, SKALE, and Solana is a fixed-amount payment path.
• Only Base provides the upto post-metering path, which depends on Permit2 approve.
• The extra.facilitatorAddress in the upto entry is the address that the client must write into the witness when signing, and it must be consistent with the value returned by the server.

¶ Base

Base uses the official USDC contract:

0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913

In the exact scheme, the client signs EIP-712 TransferWithAuthorization. The signature content includes:

• from: payer wallet address
• to: Ace Data Cloud receiving address
• value: payment amount for this transaction
• validAfter / validBefore: signature validity time window
• nonce: 32-byte random nonce

After verifying the signature, the Facilitator will call USDC's transferWithAuthorization on-chain to complete the transfer.

Base is the most recommended network for production integration, especially suitable for upto post-metering, because the Permit2, USDC, and wallet ecosystems are more mature.

Base exact verification result example:

payer 0x5d4f08D5c2bb60703284bc06671Eb680fA41B105
content ADC_BASE_E2E_OK
tx 0x408430ab3451bc22a51e510cdb4b063d6b9686724fea7a31fc109af20f5cd2f3
block 46726299
explorer https://basescan.org/tx/0x408430ab3451bc22a51e510cdb4b063d6b9686724fea7a31fc109af20f5cd2f3
transfer value 95215 atomic USDC

Result description:

• The API paid retry returns the model content ADC_BASE_E2E_OK.
• The on-chain transaction can be queried on BaseScan, and the block number is 46726299.
• 95215 atomic USDC corresponds to 0.095215 USDC, which is the actual settlement amount for this API call.

Program execution result for order payment Base exact:

order 78481793-304e-47f7-bc0c-8231aec9cc1e
state Finished
tx 0xfec08cc00a159ea1ec692b32faa9bf3d17595a986301169e689d94f58bc44151
block 46726704
explorer https://basescan.org/tx/0xfec08cc00a159ea1ec692b32faa9bf3d17595a986301169e689d94f58bc44151
transfer value 1200000 atomic USDC

Result description:

• The final status of the platform order is Finished.
• The order pay_id is written with the same Base transaction hash.
• 1200000 atomic USDC corresponds to 1.2 USDC, which is the historical actual payment amount for this 10 Credits order under the old policy; new orders no longer additionally enjoy an X402 payment method discount, and the specific signature amount is subject to this 402 response.

¶ SKALE

SKALE uses bridged USDC, with a signing method similar to Base, also EIP-3009. It is suitable for EVM payment scenarios with low gas costs; actual calls are still subject to the accepts returned by the API.

Typical 402 accepts of SKALE will include:

{
  "network": "eip155:1187947933",
  "scheme": "exact",
  "extra": {
    "name": "Bridged USDC (SKALE Bridge)",
    "version": "2",
    "chainId": 1187947933,
    "verifyingContract": "0x85889c8c714505E0c94b30fcfcF64fE3Ac8FCb20"
  }
}

SKALE currently only provides exact. If you need post-metering, please use Base upto.

SKALE exact verification result example:

content ADC_SKALE_E2E_OK
tx 0x9fd09901e74c763325fe118b2bc64765c3fca785b86b24a78b97964384db084f
block 1969317
explorer https://skale-base-explorer.skalenodes.com/tx/0x9fd09901e74c763325fe118b2bc64765c3fca785b86b24a78b97964384db084f
paid 0.095215 USDC

Result description:

• API paid retry returned model content ADC_SKALE_E2E_OK.
• The transaction can be found in SKALE explorer, and the block number is 1969317.
• The settlement amount for this exact payment is 0.095215 USDC.

¶ Solana

Solana uses SPL USDC TransferChecked. The client constructs a transfer transaction, signs and submits it, and then puts the transaction signature or serialized transaction into the PAYMENT-SIGNATURE envelope.

Characteristics of Solana:

• Uses a Solana wallet adapter or base58 secret key;
• The asset is the Solana USDC mint;
• Currently only supports exact;
• The Facilitator validates the mint, destination, authority, and amount of the transfer instruction.

If using wallet fee payer mode, the wallet directly submits the transaction, and the Facilitator is responsible for confirming the transaction and returning the settlement result.

Example of Solana exact verification result:

payer AY2RmGm2zPxB1uKvvF4dKyYdr2VySyL3wcD1MKJZoLRd
HTTP 402 -> HTTP 200
content ADC_SOLANA_E2E_OK
chain signature not confirmed in this run

Result description:

• The paid retry has returned HTTP 200, and the model output is ADC_SOLANA_E2E_OK.
• Rate limiting may be encountered when querying the on-chain signature through a public RPC.
• Because public RPC queries may be rate-limited, the Solana explorer is not listed here. When strict reconciliation is required, please use your own Solana RPC or platform-side settlement records to confirm the transaction signature.

¶ How to choose

What you want to do	Recommended network
Quickly run through the minimal flow	SKALE exact or Base exact
Target ordinary Web3 users	Base
Do post-usage metering such as chat completions	Base upto
Solana ecosystem applications	Solana exact
Low-cost EVM payment verification	SKALE exact

No matter which chain you choose, do not hardcode prices in the client. The price is determined by the accepts[].maxAmountRequired returned by the server.

¶ Added EVM networks

Native USDC fixed-amount payment is supported in code for the following networks and is being enabled one by one by network. Availability is subject to the accepts returned by the order or API; this does not mean that all networks are enabled in production.

Network	Alias	CAIP-2	Native USDC
Arbitrum One	arbitrum	eip155:42161	0xaf88d065e77c8cC2239327C5EDb3A432268e5831

These networks only support exact, and the token precision is 6. Do not use bridged USDC with the same name. When using the official TypeScript/Python X402 Client, you can pass the alias in the table or the CAIP-2 identifier. The client constructs the signature using the target chain ID; the wallet must support the target network.

The official support table for the Phantom extension wallet lists Arbitrum and Polygon; Optimism and Avalanche are currently not listed in this table, and Rabby or MetaMask that supports the target chain can be used. EVM addresses can be the same across different chains, but balances are independent of each other, and Solana addresses do not apply to EVM USDC. See the Phantom wallet support table.

¶ New network gradual rollout entry

New chain entries are hidden by default. When accessing the console or Studio, use ?features=x402-arbitrum to enable the corresponding chain; separate multiple flags with commas. To disable a single chain, use ?features=-x402-arbitrum, and to clear local overrides, use ?features=none. The switches are saved separately for each domain. Order quotes and payment retries use the same switches, and the server validates independently; existing payment records can still be viewed. Enabling only the page flag will not enable chains that have not yet been configured; the specific payable networks are still subject to real-time accepts.