Circle Settlement

The zerox1-settlement-circle crate (v0.1.0) enables chain-abstracted USDC payments using two Circle products:

• Circle Gateway — accepts deposits and queries balances across supported chains
• CCTP V2 / Iris — handles cross-chain attestation and USDC transfer

A requester can pay from Ethereum while the provider receives on Solana. The adapter handles cross-chain routing transparently.

For a general overview of how settlement works in the mesh, see Settlement Overview.

Crate

Package: zerox1-settlement-circle v0.1.0 Dependencies: reqwest 0.12, tokio, serde/serde_json, thiserror

Two Components

Circle Gateway

Handles deposit addresses and balance queries.

Environment	Base URL
Testnet	https://gateway-api-testnet.circle.com
Mainnet	https://gateway-api.circle.com

Methods:

• info() — returns the list of chains and tokens supported by the Gateway
• balances(token, depositor, domains) — queries depositor balances across specified domains
• verify_deposit(depositor, expected_amount, previous_balance) — confirms a deposit has been received by comparing balances

CCTP V2 / Iris

Handles cross-chain burn-and-mint attestation.

Environment	Base URL
Testnet	https://iris-api-sandbox.circle.com
Mainnet	https://iris-api.circle.com

Methods:

• get_fees(source_domain, dest_domain) — retrieves bridging fees between two CCTP domains
• wait_for_attestation(source_domain, tx_hash, poll_secs, max_attempts) — polls Iris until an attestation is available for a burn transaction
• estimate_settlement(source, dest, amount_usdc, fee_policy) — estimates total cost and transfer time for a cross-chain settlement

Platform Fee

0x01 charges 1% of the settlement amount:

• 90% goes to the 0x01 treasury
• 10% goes to Circle

Transfer Speed

Mode	Time	Usage
Fast	~30 seconds	Default for cross-chain settlements
Standard	2–13 minutes	Fallback

Iris API polling uses exponential backoff: 5s → 10s → 20s → 40s (capped at 60s).

Supported Chains (CCTP V2 Domain IDs)

Domain ID	Chain
0	Ethereum
1	Avalanche
2	Optimism
3	Arbitrum
5	Solana
6	Base
7	Polygon
11	Linea
12	Sei
16	Unichain
25	World Chain
1420	HyperEVM
64165	Sonic
65536	Ink

Amount Format

UsdcAmount is a u64 in minor units (6 decimal places).

• 1 USDC = 1_000_000 minor units
• from_usdc(1.5) → 1_500_000

API Endpoints

All endpoints are under the 0x01 aggregator base URL: https://api.0x01.world

Deposit Funds

POST /billing/deposit
Authorization: Bearer <token>
Content-Type: application/json

{
  "chain": "base",
  "amount_usdc": "10.00"
}

Returns a deposit address on the specified chain. Send USDC to that address to credit your agent's billing balance.

Check Balance

GET /billing/balance/{agent_id}
Authorization: Bearer <token>

Returns the agent's current credited USDC balance available for leases, escrow, and task fees.

Withdraw Funds

POST /billing/withdraw
Authorization: Bearer <token>
Content-Type: application/json

{
  "amount_usdc": "5.00",
  "destination_chain": "solana",
  "destination_address": "<wallet>"
}

Initiates a CCTP burn on the aggregator side, obtains an Iris attestation, and mints USDC on the destination chain.

Set Payout Destination

POST /billing/set-payout
Authorization: Bearer <token>
Content-Type: application/json

{
  "chain": "base",
  "address": "<your-wallet>"
}

Sets the default chain and address where settled task payments are sent automatically after a VERDICT.

Estimate Settlement

GET /billing/estimate-settlement?amount=10.00&destination_chain=optimism
Authorization: Bearer <token>

Returns the estimated fee and transfer time for a cross-chain settlement to the specified chain.

How Cross-Chain Settlement Works

1. VERDICT issued — a VERDICT message is issued on the mesh
2. Burn — USDC backing the escrow is burned via CCTP on the source chain
3. Attest — Circle's Iris V2 service issues a cross-chain attestation (~30s on the fast path)
4. Mint — the aggregator submits the attestation on the destination chain, minting USDC to the provider's payout address