Register an Operational Signer for your Wallet

Previous versions of these guides used the term delegated signer. We have moved to operational signer as the standard terminology. The next breaking API / SDK version will adopt this naming convention in method signatures and types. Until then, the code snippets below still reference addDelegatedSigner and delegatedSigners.

Register an operational signer on an existing wallet for day-to-day operations. This signer can be set up with the wallet owner — for example, a device key for user wallets or a server key for company wallets. For an overview of available signer types, see Wallet Signers.

Prerequisites

Ensure you have a wallet created.
API Key: Ensure you have an API key with the scopes: wallets:signatures.create and wallets:transactions.create.

Adding an operational signer

React
Node.js
React Native
REST

import { useWallet } from '@crossmint/client-sdk-react-ui';

const { wallet } = useWallet();

const externalSigner = {
    type: "external-wallet",
    address: "0x1234567890123456789012345678901234567890"
}

await wallet.addDelegatedSigner({
    signer: externalSigner,
});

See the React SDK reference for more details.

import { CrossmintWallets, WalletsApiClient, createCrossmint } from "@crossmint/wallets-sdk";
import { privateKeyToAccount } from "viem/accounts";

const crossmint = createCrossmint({
    apiKey: "<your-server-api-key>",
});

const crossmintWallets = CrossmintWallets.from(crossmint);
const apiClient = new WalletsApiClient(crossmint);

// The wallet's admin (recovery) signer — used to approve adding the new signer
const adminAccount = privateKeyToAccount(
    process.env.ADMIN_WALLET_PRIVATE_KEY as `0x${string}`
);

// The new operational signer to register
const operationalSignerAddress = "0x1234567890123456789012345678901234567890";

const wallet = await crossmintWallets.getWallet(
    "<wallet-address>",
    { chain: "base-sepolia", signer: { type: "external-wallet" } }
);

// 1. Add the operational signer in prepare-only mode
const { signatureId } = await wallet.addDelegatedSigner({
    signer: `external-wallet:${operationalSignerAddress}`,
    options: { experimental_prepareOnly: true },
});

// 2. Fetch the pending signature to get the message that needs signing
const delegatedSignatureResponse = await apiClient.getSignature(
    wallet.address,
    signatureId
);
if ("error" in delegatedSignatureResponse) {
    throw new Error(
        `Failed to get signature: ${JSON.stringify(delegatedSignatureResponse)}`
    );
}

const pendingApproval = delegatedSignatureResponse.approvals?.pending?.[0];
if (!pendingApproval) {
    throw new Error("No pending approval found");
}

// 3. Sign the pending approval with the admin signer's private key
//    (the wallet's original signer, not the signer being added)
const signature = await adminAccount.signMessage({
    message: { raw: pendingApproval.message as `0x${string}` },
});

// 4. Submit the approval using the admin signer
await wallet.approve({
    signatureId,
    options: {
        experimental_approval: {
            signature,
            signer: `external-wallet:${adminAccount.address}`,
        },
    },
});

console.log("Operational signer added successfully");

If the wallet’s admin (recovery) signer is an api-key type, the approval is handled automatically — you can call addDelegatedSigner without experimental_prepareOnly and skip the approval steps.

See the SDK reference for all parameters and return types.

import { useWallet } from '@crossmint/client-sdk-react-native-ui';

const { wallet } = useWallet();

const externalSigner = {
    type: "external-wallet",
    address: "0x1234567890123456789012345678901234567890"
}

await wallet.addDelegatedSigner({
    signer: externalSigner,
});

See the React Native SDK reference for more details.

Operational signers must be approved by the wallet’s recovery signer (called adminSigner in the current API). The SDK handles this automatically, but with the REST API you must approve the transaction (if using Solana, Stellar) or signature (if using EVM) to complete it.

Create the operational signer

Call the create delegated signer endpoint.

curl --request POST \
    --url https://staging.crossmint.com/api/2025-06-09/wallets/email:user@example.com:evm/signers \
    --header 'Content-Type: application/json' \
    --header 'X-API-KEY: <x-api-key>' \
    --data '{
        "chain": "base",
        "signer": "external-wallet:0x1234567890123456789012345678901234567890"
    }'

See the API reference for more details.

Sign the approval returned in the response

If you are using an api-key as the recovery signer (admin signer) you can skip the following steps.

Sign the approval message field returned in the response inside transaction.approvals (for EVM) or signature.approvals (for Solana and Stellar) using the recovery signer (admin signer).

Approve the transaction or signature to register the operational signer

EVM
Solana and Stellar

Call the approve signature endpoint using the signature from the previous step and the signature id returned in the call from Step 1.

curl --request POST \
    --url https://staging.crossmint.com/api/2025-06-09/wallets/email:user@example.com:evm/signatures/b984491a-5785-43c0-8811-45d46fe6e520/approvals \
    --header 'Content-Type: application/json' \
    --header 'X-API-KEY: <x-api-key>' \
    --data '{
        "approvals": [{
            "signer": "email:user@example.com",
            "signature": "0x1234567890abcdef..."
        }]
    }'

See the API reference for more details.

Call the approve transaction endpoint using the signature from the previous step and the transaction id returned in the call from Step 1.

curl --request POST \
    --url https://staging.crossmint.com/api/2025-06-09/wallets/email:user@example.com:solana/transactions/b984491a-5785-43c0-8811-45d46fe6e520/approvals \
    --header 'Content-Type: application/json' \
    --header 'X-API-KEY: <x-api-key>' \
    --data '{
        "approvals": [{
            "signer": "email:user@example.com",
            "signature": "5qY6wXw6zTn7..."
        }]
    }'

See the API reference for more details.

Listing all operational signers

React
Node.js
React Native
REST

import { useWallet } from '@crossmint/client-sdk-react-ui';

const { wallet } = useWallet();

const signers = await wallet.delegatedSigners();

See the React SDK reference for more details.

import { CrossmintWallets, createCrossmint } from "@crossmint/wallets-sdk";

const crossmint = createCrossmint({
    apiKey: "<your-server-api-key>",
});

const crossmintWallets = CrossmintWallets.from(crossmint);

const wallet = await crossmintWallets.getWallet(
    "<wallet-address>",
    { chain: "base-sepolia", signer: { type: "external-wallet" } }
);

const signers = await wallet.delegatedSigners();

See the SDK reference for all parameters and return types.

React Native

import { useWallet } from '@crossmint/client-sdk-react-native-ui';

const { wallet } = useWallet();

const signers = await wallet.delegatedSigners();

See the React Native SDK reference for more details.

curl --request GET \
    --url https://staging.crossmint.com/api/2025-06-09/wallets/email:user@example.com:evm \
    --header 'X-API-KEY: <x-api-key>'

See the API reference for more details.

Introduction

Quickstarts ⚡️

Concepts

Guides

API Reference

Registering a Signer

Prerequisites

Adding an operational signer

Listing all operational signers

Introduction

Quickstarts ⚡️

Concepts

Guides

API Reference

​Prerequisites

​Adding an operational signer

​Listing all operational signers

Prerequisites

Adding an operational signer

Listing all operational signers