> ## Documentation Index
> Fetch the complete documentation index at: https://docs.apiosk.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Multi-chain Settlement

> The gateway settles USDC on more than one network, how the multi-accept 402 works, how buyers pick a chain, and how publishers configure per-chain payout wallets.

# Multi-chain Settlement

The gateway settles paid calls in USDC over x402 on multiple networks. A paid
endpoint's `402` response lists one payment requirement per network the API is
configured for; the buyer picks a network, pays on it, and the publisher is paid
out on that same network.

## Supported networks

| Network  | `network` id | USDC asset                                     | Status      |
| -------- | ------------ | ---------------------------------------------- | ----------- |
| Base     | `base`       | `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`   | **Live**    |
| Solana   | `solana`     | `EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v` | **Live**    |
| Polygon  | `polygon`    | `0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359`   | Coming soon |
| Arbitrum | `arbitrum`   | `0xaf88d065e77c8cC2239327C5EDb3A432268e5831`   | Coming soon |

Polygon and Arbitrum are enabled as facilitator support lands. The currently
enabled set is published live in `meta.settlement.networks` of the discovery
document at `https://gateway.apiosk.com/.well-known/x402`, which also lists the
per-resource `accepts` entries with their networks.

## The multi-accept 402

A paid route's `402` now carries **multiple `accepts[]` entries**, one per
network the API is configured for:

* the publisher's primary network comes first
* **Base is always included** as a fallback
* any additionally configured chains follow

Every entry prices the same resource at the same USDC amount; only `network`,
`asset`, `payTo`, and `extra` differ. Solana entries carry `extra.feePayer`
(the facilitator's fee payer) instead of the EVM EIP-712 `extra.{name,version}`.

```json theme={null}
{
  "error": "Payment required",
  "accepts": [
    {
      "scheme": "exact",
      "network": "base",
      "maxAmountRequired": "60000",
      "resource": "https://gateway.apiosk.com/weather/current",
      "description": "Current weather conditions",
      "mimeType": "application/json",
      "payTo": "0x8f3C1a9bF2d47e05A6b21C9d8E4f70b3D5a6E210",
      "maxTimeoutSeconds": 60,
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "extra": { "name": "USDC", "version": "2" }
    },
    {
      "scheme": "exact",
      "network": "solana",
      "maxAmountRequired": "60000",
      "resource": "https://gateway.apiosk.com/weather/current",
      "description": "Current weather conditions",
      "mimeType": "application/json",
      "payTo": "7sPjV9dQzR4mK2xW8yBtF5cN1aHgU6eLoJpTq3ZvMnED",
      "maxTimeoutSeconds": 60,
      "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
      "extra": { "feePayer": "FaciL1tatorFeePayerPubkey11111111111111111111" }
    }
  ],
  "x402Version": 1
}
```

## How buyers choose a network

1. Read the `accepts[]` array from the `402`.
2. Pick the entry whose `network` you can pay on.
3. Sign and pay per that entry (EVM entries via the EIP-712 domain in `extra`,
   Solana entries via the facilitator fee payer in `extra.feePayer`).
4. Put the network name (`base`, `solana`, `polygon`, `arbitrum`) in the payment
   payload you send in `x-payment`: the gateway settles against the matching
   `accepts` entry.

The price is identical on every entry, so the choice is purely about which
chain your payer holds USDC on.

## Publisher payout wallets

Publishers configure settlement networks by attaching payout wallets in the
provider portal:

* attach **up to 4 payout wallets per API: exactly one per chain**, chosen
  from your verified wallets
* the connected wallet's chain is auto-detected: Base, Polygon, and Arbitrum via
  the wallet's active chain; Solana via Phantom
* wallet ownership must be verified before a wallet can be attached: EVM wallets
  sign the ownership message with an EIP-191 signature, Solana wallets sign the
  same message with Phantom (ed25519)

## Payout routing

Earnings settle to the wallet of the chain the buyer paid on: pay on Solana,
and the publisher's Solana wallet receives the payout; pay on Base, and the
Base wallet does. The split is unchanged, **98% to the publisher, 2% platform
fee**, on every network.

## Base fallback guarantee

If a network is unavailable, facilitator support is missing or the listing's
configuration for that chain is incomplete, the gateway falls back to Base
USDC. Because every `402` always includes a Base entry, **a 402 is always
payable**.

<Note>
  The SEPA Direct Debit rail is unaffected by network selection, it settles in
  euros on the bank side regardless of which chains a listing is configured for.
  See [Payment Options](/guides/payment-options).
</Note>

## Related links

* Payment model: [/overview/payment-model](/overview/payment-model)
* Payment options: [/guides/payment-options](/guides/payment-options)
* Consumer guide: [/guides/consumers](/guides/consumers)
* Bazaar discovery: [/guides/bazaar-discovery](/guides/bazaar-discovery)