Build a Transaction

Assemble a transaction message with a fee payer, a lifetime, and one or more instructions.

Solana Kit models transaction construction as a sequence of immutable transformations. This keeps the transaction pipeline easy to inspect and test.

Build a transaction message#

Transaction messages are assembled incrementally. The most common pattern is:

Create an empty message.
Set the fee payer.
Set a lifetime constraint using a recent blockhash.
Append one or more instructions.

import 'dart:typed_data';

import 'package:solana_kit/solana_kit.dart';

final rpc = createSolanaRpc(url: 'https://api.devnet.solana.com');
final feePayer = await generateKeyPair();
final latestBlockhash = await rpc.getLatestBlockhash().send();

final instruction = Instruction(
  programAddress: const Address('11111111111111111111111111111111'),
  accounts: [
    AccountMeta(address: feePayer.address, role: AccountRole.writableSigner),
  ],
  data: Uint8List(0),
);

final message = createTransactionMessage()
    .pipe(setTransactionMessageFeePayer(feePayer.address))
    .pipe(
      setTransactionMessageLifetimeUsingBlockhash(
        BlockhashLifetimeConstraint(
          blockhash: latestBlockhash.value.blockhash,
          lastValidBlockHeight: latestBlockhash.value.lastValidBlockHeight,
        ),
      ),
    )
    .pipe(appendTransactionMessageInstruction(instruction));

This separation keeps transaction construction explicit and makes it easier to reason about fee payment, expiry, and instruction ordering.

Why the lifetime constraint matters#

Without a recent blockhash or a durable nonce, the network cannot determine whether a transaction is still valid. Solana Kit makes lifetime setup explicit so expiry handling is not hidden behind a large helper.

Blockhash-based lifetime#

Use BlockhashLifetimeConstraint for the common case.

Durable nonce lifetime#

Use setTransactionMessageLifetimeUsingDurableNonce(...) when the transaction must remain valid until a nonce account changes.

Compile the message#

Once the message is fully assembled, compile it into the wire-level message representation:

final compiledMessage = compileTransactionMessage(message);

At this stage you have a canonical message layout that can be signed and serialized.

Build a Transaction