Sign a Solana transaction

signTransaction: (input: {
  transaction: SupportedSolanaTransaction;
  wallet: ConnectedStandardSolanaWallet;
  options?: SolanaSignTransactionOptions & {uiOptions?: SendTransactionModalUIOptions};
}) =>
  Promise<{
    signedTransaction: Uint8Array;
  }>;

import {useSignTransaction, useWallets} from '@privy-io/react-auth/solana';
import {pipe, createSolanaRpc, getTransactionEncoder, createTransactionMessage} from '@solana/kit';

// Inside your component
const {signTransaction} = useSignTransaction();
const {wallets} = useWallets();

const selectedWallet = wallets[0];

// Configure your connection to point to the correct Solana network
const {getLatestBlockhash} = createSolanaRpc('https://api.mainnet-beta.solana.com');

// Get the latest blockhash
const {value} = await getLatestBlockhash().send();

// Create your transaction (either legacy Transaction or VersionedTransaction)
const transaction = pipe(
  createTransactionMessage({version: 0}),
  // Set the message fee payer...
  // Set recent blockhash...
  // Add your instructions to the transaction...
  // Finally encode the transaction
  (tx) => new Uint8Array(getTransactionEncoder().encode(tx))
);

// Sign the transaction
const signedTransaction = await signTransaction({
  transaction: transaction,
  wallet: selectedWallet
});

console.log('Transaction signed successfully');

import {
  pipe,
  createTransactionMessage,
  setTransactionMessageFeePayer,
  setTransactionMessageLifetimeUsingBlockhash,
  appendTransactionMessageInstruction,
  compileTransaction,
  createSolanaRpc,
  getTransactionEncoder,
  getBase64EncodedWireTransaction,
  address,
  signatureBytes,
  type Transaction
} from '@solana/kit';
import {useSignTransaction, useWallets} from '@privy-io/react-auth/solana';

const {signTransaction} = useSignTransaction();
const {wallets} = useWallets();
const wallet = wallets[0];

const rpc = createSolanaRpc('YOUR_SOLANA_RPC_URL');
const {value: latestBlockhash} = await rpc.getLatestBlockhash().send();

// 1. Build and compile the transaction
const compiledTransaction = pipe(
  createTransactionMessage({version: 0}),
  (m) => setTransactionMessageFeePayer(address(wallet.address), m),
  (m) => setTransactionMessageLifetimeUsingBlockhash(latestBlockhash, m),
  (m) => appendTransactionMessageInstruction(/* your instruction */, m),
  (m) => compileTransaction(m)
);

// 2. Encode the compiled transaction for signing
const encodedTransaction = new Uint8Array(
  getTransactionEncoder().encode(compiledTransaction)
);

// 3. Sign via Privy — for sign-only wallets, this returns a 64-byte signature
const {signedTransaction: signature} = await signTransaction({
  transaction: encodedTransaction,
  wallet
});

// 4. Attach the signature to the compiled transaction
const signedMessage: Transaction = {
  ...compiledTransaction,
  signatures: {
    [address(wallet.address)]: signatureBytes(signature)
  }
};

// 5. Encode as a base64 wire transaction and send
await rpc
  .sendTransaction(getBase64EncodedWireTransaction(signedMessage), {
    preflightCommitment: 'confirmed',
    encoding: 'base64'
  })
  .send();