> ## 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.

# How-to: Add another wallet owner

> Register an additional passkey as an authorized owner on your MSCA to extend recovery coverage across additional devices.

Register an additional
[WebAuthn](https://developer.mozilla.org/en-US/docs/Web/API/Web_Authentication_API)
passkey as an owner on your
[modular smart contract account (MSCA)](/wallets/account-types#smart-contract-accounts-sca-and-msca).
Additional owners serve as recovery keys. They extend recovery coverage across
additional devices without changing how routine signing works. See
[How Digital Asset-Backed Borrowing works](/circle-mint/concepts/digital-asset-backed-borrowing)
for the wallet architecture.

## Prerequisites

Before you begin, ensure that you've:

* Completed the
  [Borrow USDC against cirBTC collateral](/circle-mint/quickstarts/borrow-with-cirbtc)
  quickstart and provisioned a wallet.
* Registered a new WebAuthn passkey on the device you want to add as an owner.
  Capture the P-256 public key and the WebAuthn credential identifier as hex
  strings.

## Steps

<Steps>
  <Step title="Submit the add-owner request">
    Call
    [`POST /v1/borrow/wallets/owners`](/api-reference/circle-mint/digital-asset-backed-borrowing/add-borrow-wallet-owner)
    with the new passkey's public key and credential ID.

    ```bash theme={null}
    curl -X POST https://api-sandbox.circle.com/v1/borrow/wallets/owners \
      -H "Authorization: Bearer $API_KEY" \
      -H "Content-Type: application/json" \
      -d '{
        "idempotencyKey": "f7a8b9c0-d123-4e56-7890-abcdef123456",
        "ownerKey": "0x04c1d2e3f4051627384950a1b2c3d4e5f60718293a4b5c6d7e8f90a1b2c3d4e5f6",
        "credentialId": "b2c3d4e5f6071829"
      }'
    ```

    The endpoint returns an `onchainJob` with `jobType: add_owner`:

    ```json theme={null}
    {
      "data": {
        "id": "a7b8c9d0-e123-4567-890a-bcdef1234567",
        "jobType": "add_owner",
        "status": "received",
        "createDate": "2026-06-25T11:00:00.000Z",
        "updateDate": "2026-06-25T11:00:00.000Z"
      }
    }
    ```

    Save the job `id`. You poll it in the next step.
  </Step>

  <Step title="Wait for the operation to complete">
    Poll
    [`GET /v1/borrow/jobs/{id}`](/api-reference/circle-mint/digital-asset-backed-borrowing/get-borrow-job)
    until `status` reaches `completed`.

    ```json theme={null}
    {
      "data": {
        "id": "a7b8c9d0-e123-4567-890a-bcdef1234567",
        "jobType": "add_owner",
        "status": "completed",
        "txHash": "0x4d5e6f70819293a4b5c6d7e8f90a1b2c3d4e5f60718293a4b5c6d7e8f9aabbccdd",
        "createDate": "2026-06-25T11:00:00.000Z",
        "updateDate": "2026-06-25T11:01:30.000Z"
      }
    }
    ```
  </Step>

  <Step title="Confirm the new owner">
    Fetch the wallet and confirm the new owner appears in the `owners` array with
    `status: active`:

    ```bash theme={null}
    curl https://api-sandbox.circle.com/v1/borrow/wallets \
      -H "Authorization: Bearer $API_KEY"
    ```

    ```json theme={null}
    {
      "data": [
        {
          "id": "9c1b2a3d-4e5f-6071-8293-a4b5c6d7e8f9",
          "walletAddress": "0x742d35Cc6634C0532925a3b844Bc9e7595f9f68C",
          "owners": [
            {
              "id": "1f2e3d4c-5b6a-7980-1234-56789abcdef0",
              "ownerType": "passkey",
              "publicKey": "0x04b0a1c2d3e4f5061728394a5b6c7d8e9f00112233445566778899aabbccddeeff",
              "credentialId": "a1b2c3d4e5f60718",
              "status": "active",
              "addedDate": "2026-06-20T14:10:00.000Z"
            },
            {
              "id": "2e3d4c5b-6a79-8012-3456-789abcdef012",
              "ownerType": "passkey",
              "publicKey": "0x04c1d2e3f4051627384950a1b2c3d4e5f60718293a4b5c6d7e8f90a1b2c3d4e5f6",
              "credentialId": "b2c3d4e5f6071829",
              "status": "active",
              "addedDate": "2026-06-25T11:01:30.000Z"
            }
          ]
        }
      ]
    }
    ```

    The wallet now has two passkey recovery owners. Circle's ECDSA co-signer
    continues to sign every UserOperation for the wallet. The additional passkey
    does not change routine signing behavior.
  </Step>
</Steps>