Sending sponsored Solana transactions

The SDK primarily abstracts three endpoints: prepare_sol_transaction, sol_send_transaction, and get_send_transaction_status (plus Gas Station usage / limits for sponsorship budgets). You can sign and broadcast Solana transactions in two primary ways:

Using the React handler (handleSendTransaction) from @0xkey-io/react-wallet-kit This gives you:
- modals
- spinner + chain logo
- success screen
- explorer link
- built-in polling
Using low-level functions in @0xkey-io/core / @0xkey-io/sdk-server You manually call:
- prepareSolTransaction → build unsigned message (set sponsor: true for fee sponsorship)
- solSendTransaction → submit
- pollTransactionStatus / getSendTransactionStatus → wait for confirmation

This page walks you through sponsored custodial sends. For EVM Gas Station (EIP-7702), see Sending sponsored EVM transactions.

Fee sponsorship (sponsor: true) uses a platform Solana fee-payer as account_keys[0]. Review Solana transaction construction for sponsored flows before submitting third-party or router-built payloads.

How Solana fee sponsorship works

Solana sponsorship is not EIP-7702. 0xkey inserts a platform fee-payer as account_keys[0] and requires the user wallet as the second required signer on the same transaction (custodial dual-sign). Your users do not need SOL for fees; 0xkey pays them and records usage against your Gas Station limits (lamports).

Mode	Who pays fees	Who signs
`sponsor: false`	User wallet (`account_keys[0]`)	User only
`sponsor: true`	Platform fee-payer (`account_keys[0]`)	User (`account_keys[1]`) + platform fee-payer

Enable Gas Station in the 0xkey dashboard and configure Solana spend limits before using sponsor: true. Self-paid sends (sponsor: false) do not require Gas Station.

For payload constraints (program whitelist, account-creation rules, ALT), see Solana transaction construction for sponsored flows.

Prepare then send (recommended)

Call prepareSolTransaction with sponsor: true so the unsigned message places the platform fee-payer at index 0 and the user at index 1.
Submit solSendTransaction with the same sponsor: true, signWith set to the user address, and the unsigned transaction hex from prepare (or an equivalent message you built with the same account ordering).

import { ZeroXKeyClient } from "@0xkey-io/sdk-server"; // or @0xkey-io/core

const client = new ZeroXKeyClient({ /* apiBaseUrl, organizationId, stamper */ });

const prepared = await client.prepareSolTransaction({
  organizationId,
  from: userSolanaAddress,
  to: recipientAddress,
  amount: "1000000", // lamports
  caip2: "solana:devnet",
  sponsor: true,
});

const { activity } = await client.solSendTransaction({
  type: "ACTIVITY_TYPE_SOL_SEND_TRANSACTION",
  timestampMs: String(Date.now()),
  organizationId,
  parameters: {
    signWith: userSolanaAddress,
    unsignedTransaction: prepared.unsignedTransaction,
    caip2: "solana:devnet",
    sponsor: true,
  },
});

const statusId = activity.result?.solSendTransactionResult?.sendTransactionStatusId;

Dashboard Send uses the same flow via the dashboard gateway (POST /api/v1/sol_send_transaction) with WebAuthn / stamp auth.

Using `handleSendTransaction` (React)

When your React kit build exposes Solana send with sponsorship:

const { handleSendTransaction, wallets } = useZeroXKey();

const walletAccount = wallets
  .flatMap((w) => w.accounts)
  .find((a) => a.addressFormat === "ADDRESS_FORMAT_SOLANA");

if (!walletAccount) {
  throw new Error("No Solana wallet account found");
}

await handleSendTransaction({
  transaction: {
    signWith: walletAccount.address,
    unsignedTransaction: "<hex-serialized-unsigned-solana-tx>",
    caip2: "solana:devnet",
    sponsor: true,
  },
});

Prefer building unsignedTransaction with prepareSolTransaction({ sponsor: true }) so fee-payer ordering matches what the coordinator validates.

Checking usage and limits

Gas Station tracks Solana sponsorship in lamports (separate from EVM wei limits). Query usage via Gas Station / gas-usage APIs and configure window limits in the dashboard.

const usage = await client.getGasUsage({ organizationId });
// Enforce client-side UX when approaching windowLimit* fields for Solana

Policy notes

Sponsored and self-paid Solana sends both flow through the enclave parser and policy engine (solana.tx.*). With sponsor: true, policy binding allows signWith to be a non-fee-payer required signer (account_keys[1..)), and may require feePayer to match account_keys[0]. See Solana policy examples and Solana overview.

Next steps

Solana (SVM) support
Solana transaction construction for sponsored flows
Sending sponsored EVM transactions (EIP-7702 Gas Station — different mechanism)

Get started

Products

Crypto ecosystems

Developers

Sending sponsored Solana transactions

How Solana fee sponsorship works

Prepare then send (recommended)

Using `handleSendTransaction` (React)

Checking usage and limits

Policy notes

Next steps

​How Solana fee sponsorship works

​Prepare then send (recommended)

​Using handleSendTransaction (React)

​Checking usage and limits

​Policy notes

​Next steps

How Solana fee sponsorship works

Prepare then send (recommended)

Using `handleSendTransaction` (React)

Checking usage and limits

Policy notes

Next steps