> ## Documentation Index
> Fetch the complete documentation index at: https://ramps-04-30-docs-add-grid-tutorial-skill-interactive-zero-t.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Implementation overview

> End-to-end walkthrough: create a customer, find their Global Account, register a passkey, fund the account, and execute a signed withdrawal.

## Prerequisites

<Warning>
  Customers who hold a Global Account must be KYC/KYB verified before any account funds can move from or to fiat rails. This quickstart picks up after KYC is complete.

  In sandbox, customers are automatically KYC approved on creation so you can skip straight to account setup.
</Warning>

You also need:

* A platform configured with `USDB` in its supported currencies. In sandbox, USDB is enabled by default alongside `USD` and `USDC`.
* Sandbox or production API credentials with access to the `Embedded Wallet Auth` and `Internal Accounts` endpoints.

```bash theme={null}
export GRID_BASE_URL="https://api.lightspark.com/grid/2025-10-13"
export GRID_CLIENT_ID="YOUR_SANDBOX_CLIENT_ID"
export GRID_CLIENT_SECRET="YOUR_SANDBOX_CLIENT_SECRET"
```

## Walkthrough

The walkthrough below is the happy path: create a customer, find the auto-provisioned account, register a passkey, fund it, and withdraw to a bank account. Each step shows the HTTP request your integrator backend makes on behalf of the client.

### 1. Create a customer

Create the customer record. A Global Account is provisioned automatically whenever a customer is created on a platform that has `USDB` in its supported currencies — you don't need to pass it on the customer.

```bash theme={null}
curl -X POST "$GRID_BASE_URL/customers" \
  -u "$GRID_CLIENT_ID:$GRID_CLIENT_SECRET" \
  -H "Content-Type: application/json" \
  -d '{
    "customerType": "INDIVIDUAL",
    "platformCustomerId": "ind-9f84e0c2",
    "region": "US",
    "email": "jane@example.com",
    "fullName": "Jane Doe",
    "birthDate": "1990-01-15",
    "nationality": "US"
  }'
```

**Response:** `201 Created` with the new `Customer:...` id. In sandbox, the customer is KYC-approved immediately; in production you would now run them through the KYC / KYB flow before any funds can move.

### 2. Find the Global Account

When a customer is created on a USDB-enabled platform, Grid automatically provisions a Global Account alongside their other internal accounts. Fetch it by filtering the customer's internal accounts by `type=EMBEDDED_WALLET`.

```bash theme={null}
curl -X GET "$GRID_BASE_URL/internal-accounts?customerId=Customer:019542f5-b3e7-1d02-0000-000000000001&type=EMBEDDED_WALLET" \
  -u "$GRID_CLIENT_ID:$GRID_CLIENT_SECRET"
```

**Response:**

```json theme={null}
{
  "data": [
    {
      "id": "InternalAccount:019542f5-b3e7-1d02-0000-000000000002",
      "customerId": "Customer:019542f5-b3e7-1d02-0000-000000000001",
      "type": "EMBEDDED_WALLET",
      "balance": {
        "amount": 0,
        "currency": {
          "code": "USDB",
          "name": "USDB",
          "decimals": 6
        }
      },
      "fundingPaymentInstructions": [],
      "createdAt": "2026-04-19T12:00:00Z",
      "updatedAt": "2026-04-19T12:00:00Z"
    }
  ],
  "hasMore": false,
  "totalCount": 1
}
```

Hold onto the `InternalAccount:...` id — every auth credential is scoped to it.

### 3. Register a passkey credential

Global Accounts support three authentication credential types: **passkey**, **OAuth (OIDC)**, and **email OTP**. A passkey is a user-friendly default: biometric, phishing-resistant, and usable across the user's devices.

Registration only binds the passkey to the account — it doesn't issue a session. Sessions are created on-demand, when the customer initiates an action that needs a signature (step 7). The full flow with sequence diagram is documented in <a href="authentication#passkey-registration">Authentication</a>; the condensed version:

<Steps>
  <Step title="Your backend issues a WebAuthn challenge">
    Generate a random base64url `challenge`, store it short-lived in your session store, and return it to the client.
  </Step>

  <Step title="Client runs `navigator.credentials.create()` / platform equivalent">
    The browser or OS prompts the user for a biometric, returns an `attestation`. The client posts the attestation back to your backend.
  </Step>

  <Step title="Your backend calls Grid">
    ```bash theme={null}
    curl -X POST "$GRID_BASE_URL/auth/credentials" \
      -u "$GRID_CLIENT_ID:$GRID_CLIENT_SECRET" \
      -H "Content-Type: application/json" \
      -d '{
        "type": "PASSKEY",
        "accountId": "InternalAccount:019542f5-b3e7-1d02-0000-000000000002",
        "nickname": "iPhone Face-ID",
        "challenge": "ArkQi2yAYHPlgnJNFBlneIwchQdWXBOTrdB-AmMUB21Lx",
        "attestation": {
          "credentialId": "AdKXJEch1aV5Wo7bj7qLHskVY4OoNaj9qu8TPdJ7kSAgUeRxWNngXlcNIGt4gexZGKVGcqZpqqWordXb_he1izY",
          "clientDataJson": "eyJjaGFsbGVuZ2UiOiJBcktRaTJ5...",
          "attestationObject": "o2NmbXRkbm9uZWdhdHRTdG10...",
          "transports": ["internal", "hybrid"]
        }
      }'
    ```

    Grid verifies the attestation and replies `201` with the new `AuthMethod:...` id plus the first-authentication `challenge`, `requestId`, and `expiresAt`. Persist the auth method id against the customer — you'll pass it to `/challenge` and `/verify` whenever the customer needs to sign.
  </Step>
</Steps>

The passkey is now bound to the account. You'll use it to authorize the withdrawal in step 7.

### 4. Fund the Account

Global Accounts behave like any other internal account on the way in — incoming funds do not need the customer's signature. In sandbox, use the sandbox funding endpoint to skip straight to a funded state:

```bash theme={null}
curl -X POST "$GRID_BASE_URL/sandbox/internal-accounts/InternalAccount:019542f5-b3e7-1d02-0000-000000000002/fund" \
  -u "$GRID_CLIENT_ID:$GRID_CLIENT_SECRET" \
  -H "Content-Type: application/json" \
  -d '{
    "amount": 1000000000
  }'
```

`amount` is in the smallest unit of the account's currency. USDB has 6 decimals, so `1000000000` is 1,000.00 USDB.

You will receive an `INCOMING_PAYMENT` webhook when the balance updates. The account now holds 1,000.00 USDB.

<Tip>
  To fund from another currency (USD ACH, USDC on-chain, etc.), create a quote with `destination.destinationType: "ACCOUNT"` pointing at the Global Account's `InternalAccount` id. The quote's `sourceCurrency` can be any supported platform currency; Grid will convert into USDB on execute.
</Tip>

### 5. Add an external bank account

Add the destination the customer wants to withdraw to. This is a standard external account — nothing Global Account-specific.

```bash theme={null}
curl -X POST "$GRID_BASE_URL/customers/external-accounts" \
  -u "$GRID_CLIENT_ID:$GRID_CLIENT_SECRET" \
  -H "Content-Type: application/json" \
  -d '{
    "customerId": "Customer:019542f5-b3e7-1d02-0000-000000000001",
    "currency": "USD",
    "platformAccountId": "jane_doe_checking",
    "accountInfo": {
      "accountType": "USD_ACCOUNT",
      "accountNumber": "1234567890",
      "routingNumber": "021000021",
      "beneficiary": {
        "beneficiaryType": "INDIVIDUAL",
        "fullName": "Jane Doe",
        "birthDate": "1990-01-15",
        "nationality": "US",
        "address": {
          "line1": "123 Main Street",
          "city": "San Francisco",
          "state": "CA",
          "postalCode": "94105",
          "country": "US"
        }
      }
    }
  }'
```

**Response:** `201 Created` with the new `ExternalAccount:...` id.

### 6. Create a withdrawal quote

Create a quote with the Global Account as the source. Grid returns a `payloadToSign` in the quote's payment instructions — this is what the client will sign to authorize the transfer.

```bash theme={null}
curl -X POST "$GRID_BASE_URL/quotes" \
  -u "$GRID_CLIENT_ID:$GRID_CLIENT_SECRET" \
  -H "Content-Type: application/json" \
  -d '{
    "source": {
      "sourceType": "ACCOUNT",
      "accountId": "InternalAccount:019542f5-b3e7-1d02-0000-000000000002"
    },
    "destination": {
      "destinationType": "ACCOUNT",
      "accountId": "ExternalAccount:a12dcbd6-dced-4ec4-b756-3c3a9ea3d123"
    },
    "lockedCurrencySide": "SENDING",
    "lockedCurrencyAmount": 10000000,
    "description": "Withdrawal to checking"
  }'
```

`lockedCurrencyAmount` is in the smallest unit of the locked side's currency. Here the sending currency is USDB (6 decimals), so `10000000` is 10.00 USDB.

**Response:**

```json theme={null}
{
  "id": "Quote:019542f5-b3e7-1d02-0000-000000000006",
  "status": "PENDING",
  "createdAt": "2026-04-19T12:05:00Z",
  "expiresAt": "2026-04-19T12:10:00Z",
  "source": {
    "accountId": "InternalAccount:019542f5-b3e7-1d02-0000-000000000002",
    "currency": "USDB"
  },
  "destination": {
    "accountId": "ExternalAccount:a12dcbd6-dced-4ec4-b756-3c3a9ea3d123",
    "currency": "USD"
  },
  "sendingCurrency": { "code": "USDB", "name": "USDB", "decimals": 6 },
  "receivingCurrency": { "code": "USD", "name": "United States Dollar", "symbol": "$", "decimals": 2 },
  "totalSendingAmount": 10000000,
  "totalReceivingAmount": 975,
  "exchangeRate": 1.0,
  "feesIncluded": 250000,
  "transactionId": "Transaction:019542f5-b3e7-1d02-0000-000000000005",
  "paymentInstructions": [
    {
      "accountOrWalletInfo": {
        "accountType": "EMBEDDED_WALLET",
        "payloadToSign": "{\"type\":\"ACTIVITY_TYPE_SIGN_TRANSACTION_V2\",\"timestampMs\":\"1746736509954\",\"organizationId\":\"org_abc123\",\"parameters\":{\"signWith\":\"wallet_abc123def456\",\"unsignedTransaction\":\"ea69b4bf05f775209f26ff0a34a05569180f7936579d5c4af9377ae550194f72\",\"type\":\"TRANSACTION_TYPE_ETHEREUM\"},\"generateAppProofs\":true}"
      },
      "instructionsNotes": "Sign the payloadToSign byte-for-byte and pass the signature as the Grid-Wallet-Signature header on execute"
    }
  ]
}
```

### 7. Authenticate and sign

The customer has an outstanding quote with a `payloadToSign`. Now we need a session signing key to sign it with — this is when the passkey actually gets used. The flow is keypair → challenge → assertion → verify → decrypt → sign.

<Steps>
  <Step title="Your backend requests a fresh challenge sealed to the client public key">
    The client generates a fresh <a href="client-keys#1-generate-a-client-key-pair">P-256 client key pair</a> and posts the public key (uncompressed hex) to your backend, which forwards it to Grid. Grid bakes the public key into the session-creation payload so the resulting session signing key is sealed to that device.

    ```bash theme={null}
    curl -X POST "$GRID_BASE_URL/auth/credentials/AuthMethod:019542f5-b3e7-1d02-0000-000000000001/challenge" \
      -u "$GRID_CLIENT_ID:$GRID_CLIENT_SECRET" \
      -H "Content-Type: application/json" \
      -d '{
        "clientPublicKey": "04f45f2a22c908b9ce09a7150e514afd24627c401c38a4afc164e1ea783adaaa31d4245acfb88c2ebd42b47628d63ecabf345484f0a9f665b63c54c897d5578be2"
      }'
    ```

    **Response (200):**

    ```json theme={null}
    {
      "id": "AuthMethod:019542f5-b3e7-1d02-0000-000000000001",
      "accountId": "InternalAccount:019542f5-b3e7-1d02-0000-000000000002",
      "type": "PASSKEY",
      "nickname": "iPhone Face-ID",
      "createdAt": "2026-04-19T12:00:01Z",
      "updatedAt": "2026-04-19T12:05:00Z",
      "challenge": "VjZ6o8KfE9V3q3LkR2nH5eZ6dM8yA1xW",
      "requestId": "7c4a8d09-ca37-4e3e-9e0d-8c2b3e9a1f21",
      "expiresAt": "2026-04-19T12:10:00Z"
    }
    ```

    Return `challenge` and `requestId` to the client.
  </Step>

  <Step title="Client runs the WebAuthn assertion against the Grid-issued challenge">
    Prompt the authenticator with the `challenge` returned in the previous step:

    ```js theme={null}
    const base64urlToBytes = (value) => {
      const padded = value.replace(/-/g, "+").replace(/_/g, "/")
        .padEnd(Math.ceil(value.length / 4) * 4, "=");
      return Uint8Array.from(atob(padded), (char) => char.charCodeAt(0));
    };

    const assertion = await navigator.credentials.get({
      publicKey: {
        challenge: base64urlToBytes(gridChallenge),
        rpId: "yourapp.com",
        userVerification: "required",
      },
    });
    ```

    Post the assertion (and the `requestId` from the previous step) back to your backend.
  </Step>

  <Step title="Your backend verifies the assertion with Grid to mint a session">
    ```bash theme={null}
    curl -X POST "$GRID_BASE_URL/auth/credentials/AuthMethod:019542f5-b3e7-1d02-0000-000000000001/verify" \
      -u "$GRID_CLIENT_ID:$GRID_CLIENT_SECRET" \
      -H "Content-Type: application/json" \
      -H "Request-Id: 7c4a8d09-ca37-4e3e-9e0d-8c2b3e9a1f21" \
      -d '{
        "type": "PASSKEY",
        "assertion": {
          "credentialId": "KEbWNCc7NgaYnUyrNeFGX9_3Y-8oJ3KwzjnaiD1d1LVTxR7v3CaKfCz2Vy_g_MHSh7yJ8yL0Pxg6jo_o0hYiew",
          "clientDataJson": "eyJjaGFsbGVuZ2UiOiJWalo2bzhLZkU5VjNxM0xrUjJuSDVlWjZkTTh5QTF4VyIsIm9yaWdpbiI6Imh0dHBzOi8veW91cmFwcC5jb20iLCJ0eXBlIjoid2ViYXV0aG4uZ2V0In0",
          "authenticatorData": "PdxHEOnAiLIp26idVjIguzn3Ipr_RlsKZWsa-5qK-KABAAAAkA",
          "signature": "MEUCIQDYXBOpCWSWq2Ll4558GJKD2RoWg958lvJSB_GdeokxogIgWuEVQ7ee6AswQY0OsuQ6y8Ks6jhd45bDx92wjXKs900"
        }
      }'
    ```

    `clientPublicKey` is no longer required here — Grid already has it from the `/challenge` call. The `Request-Id` header ties this verify to that earlier challenge.

    **Response (200):**

    ```json theme={null}
    {
      "id": "Session:019542f5-b3e7-1d02-0000-000000000003",
      "accountId": "InternalAccount:019542f5-b3e7-1d02-0000-000000000002",
      "type": "PASSKEY",
      "nickname": "iPhone Face-ID",
      "encryptedSessionSigningKey": "w99a5xV6A75TfoAUkZn869fVyDYvgVsKrawMALZXmrauZd8hEv66EkPU1Z42CUaHESQjcA5bqd8dynTGBMLWB9ewtXWPEVbZvocB4Tw2K1vQVp7uwjf",
      "createdAt": "2026-04-19T12:05:01Z",
      "updatedAt": "2026-04-19T12:05:01Z",
      "expiresAt": "2026-04-19T12:20:01Z"
    }
    ```

    Return `encryptedSessionSigningKey` and `expiresAt` to the client.
  </Step>

  <Step title="Client decrypts the session signing key and signs the payload">
    The client <a href="client-keys#3-decrypt-the-session-signing-key">decrypts</a> `encryptedSessionSigningKey` with the matching client private key, then <a href="client-keys#4-sign-a-payloadtosign">signs the quote's `payloadToSign`</a> with the resulting session signing key. Return the base64 signature to your backend.
  </Step>
</Steps>

<Warning>
  Sign the `payloadToSign` bytes exactly as Grid returned them. Do not parse, re-serialize, trim, or normalize the JSON — the signature must cover the same bytes Grid's verifier hashes.
</Warning>

The session signing key is now valid for 15 minutes, so subsequent account actions within that window (for example, a second withdrawal) can reuse it without another `/challenge` + `/verify` round-trip.

### 8. Execute the quote

Call `/execute` with the signature in the `Grid-Wallet-Signature` header.

```bash theme={null}
curl -X POST "$GRID_BASE_URL/quotes/Quote:019542f5-b3e7-1d02-0000-000000000006/execute" \
  -u "$GRID_CLIENT_ID:$GRID_CLIENT_SECRET" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: 7c4a8d09-ca37-4e3e-9e0d-8c2b3e9a1f21" \
  -H "Grid-Wallet-Signature: MEUCIQDx7k2N0aK4p8f3vR9J6yT5wL1mB0sXnG2hQ4vJ8zYkCgIgZ4rP9dT7eWfU3oM6KjR1qSpNvBwL0tXyA2iG8fH5dE="
```

**Response:**

```json theme={null}
{
  "id": "Quote:019542f5-b3e7-1d02-0000-000000000006",
  "status": "PROCESSING",
  "transactionId": "Transaction:019542f5-b3e7-1d02-0000-000000000005",
  "totalSendingAmount": 10000000,
  "totalReceivingAmount": 975,
  "feesIncluded": 250000
}
```

The transaction is on its way. You'll receive standard transaction webhooks (`OUTGOING_PAYMENT`) as it settles — see [Transaction lifecycle](/platform-overview/core-concepts/transaction-lifecycle).

## Where to next

<CardGroup cols={2}>
  <Card title="Client keys & signing" href="./client-keys" icon="key">
    Generate the P-256 key pair, decrypt the session signing key, and sign payloads on Web, iOS, and Android.
  </Card>

  <Card title="Authentication" href="./authentication" icon="shield-check">
    OAuth and Email OTP flows, passkey reauthentication, and the full WebAuthn parameter mapping.
  </Card>

  <Card title="Sessions" href="./managing-sessions" icon="clock-rotate-left">
    List active sessions and revoke a session (sign-out).
  </Card>

  <Card title="Exporting a wallet" href="./exporting-wallet" icon="file-export">
    Let a customer take their wallet seed off Grid.
  </Card>
</CardGroup>