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

# Supported networks

> Identifiers and USDC contracts for the blockchains Facilitator Service supports

## Blockchains

* Arc
* Base
* Polygon PoS

## Identifiers and contracts

Use the `CAIP-2` value as the `network` field and the USDC contract as the
`asset` field in your x402 `paymentRequirements`.

### Mainnet

| Blockchain  | CAIP-2        | USDC contract                                |
| ----------- | ------------- | -------------------------------------------- |
| Arc         | `eip155:5042` | `0x3600000000000000000000000000000000000000` |
| Base        | `eip155:8453` | `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913` |
| Polygon PoS | `eip155:137`  | `0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359` |

### Testnet

| Blockchain       | CAIP-2           | USDC contract                                |
| ---------------- | ---------------- | -------------------------------------------- |
| Arc              | `eip155:5042002` | `0x3600000000000000000000000000000000000000` |
| Base Sepolia     | `eip155:84532`   | `0x036CbD53842c5426634e7929541eC2318f3dCF7e` |
| Polygon PoS Amoy | `eip155:80002`   | `0x41E94Eb019C0762f9Bfcf9Fb1E58725BfB0e7582` |

## Confirmation thresholds

Facilitator Service reports
[`/settle`](/api-reference/agent-stack/facilitator-service/settle-payment) and
[`/status`](/api-reference/agent-stack/facilitator-service/get-payment-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.