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Documentation Index

Fetch the complete documentation index at: https://www.dynamic.xyz/docs/llms.txt

Use this file to discover all available pages before exploring further.

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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.

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Prerequisites

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.

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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

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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.

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Next Steps