Knit API Documentation

CPN Onboarding Checklist

This checklist maps Circle CPN V2 requirements to Knit's Managed Signing API.

Overview

Step 1: Create a Managed Signing Wallet

Create a wallet that will hold funds and sign CPN transactions.

Production:

{
  "type": "EVM",
  "networks": ["MATIC_MAINNET"]
}

Testing (Sandbox/Dev):

{
  "type": "EVM",
  "networks": ["MATIC_AMOY"]
}

See: Create Wallet

Step 2: Create a CPN Policy

Configure policy rules that allow CPN V2 signature flows.

Production:

{
  "name": "cpn-v2",
  "rules": {
    "chains": ["MATIC_MAINNET"],
    "tokens": ["<USDC token address>"],
    "spenders": ["<Permit2 contract address>"],
    "typedData": { "allow": true },
    "denyUnlimitedApprovals": false,
    "allowRawTx": false
  }
}

Testing (Sandbox/Dev):

{
  "name": "cpn-v2-test",
  "rules": {
    "chains": ["MATIC_AMOY"],
    "tokens": ["<USDC testnet token address>"],
    "spenders": ["<Permit2 testnet contract address>"],
    "typedData": { "allow": true },
    "denyUnlimitedApprovals": false,
    "allowRawTx": false
  }
}

See: Create Policy

Step 3: One-Time Permit2 Approval

Approve the Permit2 contract to spend USDC on behalf of your wallet.

{
  "walletId": "<wallet-id>",
  "network": "MATIC_MAINNET",
  "type": "evm_tx",
  "kind": "erc20_approve",
  "payload": {
    "token": "<USDC token address>",
    "spender": "<Permit2 contract address>",
    "amount": "<approval amount>"
  },
  "broadcast": true
}

For testing, use MATIC_AMOY network with testnet token/contract addresses.

See: Permit2 Approval

Step 4: Per-Payment Signature

For each payment, Circle provides messageToBeSigned (EIP-712 typed data). Sign it and return the signature.

{
  "walletId": "<wallet-id>",
  "network": "MATIC_MAINNET",
  "type": "eip712",
  "payload": {
    "typedData": { "...Circle's messageToBeSigned..." }
  }
}

For testing, use MATIC_AMOY network.

See: Per-Payment Signature

(Optional) Step 5: CPN V1 Raw Transaction

Only needed for legacy CPN V1 integration.

See: CPN V1 Raw TX

Key Addresses

Production Networks

Testnet Networks (Sandbox/Dev)

Contact Circle or refer to their documentation for the exact contract addresses for your integration.

Note: Most merchants test CPN integration using MATIC_AMOY testnet before moving to production.