Sponsor SVM Transactions

Overview

DynamicSvmWalletClient::sponsorTransaction is the lower-level primitive behind sponsored transactions. It takes the serialized message of an unsigned transaction and returns the sponsor-signed wire envelope — the sponsor’s signature is pre-filled in slot 0, the user signature slots are zeroed, and the original message is appended. Most apps don’t need this directly — use sendTransaction(...).sponsor(true) for the one-shot sign + sponsor + broadcast flow. Reach for sponsorTransaction when you want to:

Have the user sign the sponsor-prepped envelope on a separate path (client-side wallet, hardware wallet)
Inspect or audit the sponsor signature before adding the user signature
Batch sponsorship outside Dynamic’s broadcast path

Gas sponsorship must be enabled for your environment in the Dynamic dashboard before calls succeed.

Prerequisites

Created an SVM wallet
Gas sponsorship enabled in the Dashboard

byte[] messageBytes  = /* bytes(transaction.message) */;
byte[] sponsoredWire = client.sponsorTransaction(messageBytes).join();

sponsoredWire layout:

[compact-u16 sigCount][sigCount × 64-byte slots, sponsor pre-filled, user zeroed][sponsored message]

The sponsor signature occupies slot 0; every other signature slot is zeroed and waiting for the corresponding signer.

Filling in the User Signature

If your wallet’s account index is idx (typically 1 for a single user signer after the sponsor), overwrite that 64-byte slot with the user’s Ed25519 signature, then push to RPC:

import org.web3j.utils.Numeric;

byte[] sigBytes = Numeric.hexStringToByteArray("0x" + userSignatureHex);  // 64 bytes
System.arraycopy(sigBytes, 0, sponsoredWire, /* offset of slot idx */, 64);

// Push to any Solana RPC
solanaRpc.sendRawTransaction(sponsoredWire);

To compute the offset of slot idx:

offset = compactU16Length(sigCount) + idx * 64

Pairing with the MPC Signer

The most common pattern: sponsor first (no MPC needed), then run signTransaction over the same messageBytes to get the user’s Ed25519 signature, then splice it into the sponsored envelope:

byte[] sponsoredWire = client.sponsorTransaction(messageBytes).join();

String userSigHex = client.signTransaction(SignTransactionOpts.builder()
    .messageBytes(messageBytes)
    .walletProperties(walletProperties)
    .externalServerKeyShares(externalServerKeyShares)
    .build()
).join();

byte[] userSig = Numeric.hexStringToByteArray("0x" + userSigHex);
System.arraycopy(userSig, 0, sponsoredWire, userSigOffset, 64);

// Broadcast sponsoredWire via your preferred Solana RPC client.

For the streamlined version of this — sponsor + sign + broadcast in a single SDK call — see sendTransaction with sponsor=true.

Next Steps

Send transactions — sign + sponsor + broadcast in one call
Sign transactions
Sign messages
Delegated access

Getting Started

EVM Guides

SVM Guides

Lifecycle

Sponsor SVM Transactions

Overview

Prerequisites

Filling in the User Signature

Pairing with the MPC Signer

Next Steps

​Overview

​Prerequisites

​Sponsor a Message

​Filling in the User Signature

​Pairing with the MPC Signer

​Next Steps

Overview

Prerequisites

Sponsor a Message

Filling in the User Signature

Pairing with the MPC Signer

Next Steps