Unified Tx API

Preview feature: available in 0.8.0 previews. See the latest preview. APIs may change before the stable release.

What Changed

In previous versions, building transactions required choosing between two classes:

• Tx — for regular payments, native token minting, staking, and governance
• ScriptTx — for Plutus script inputs, Plutus minting, and validator attachment

In the 0.8.0 previews, all ScriptTx operations are also available directly on Tx, and ScriptTx is deprecated. It isn’t deprecated in the stable 0.7.x releases, where it’s still how you build script transactions, and it still works in the previews.

Why

• No more class-choice burden — you don’t need to decide upfront whether your transaction involves scripts
• Mix operations freely — combine script inputs, Plutus minting, native payments, and staking in a single Tx
• Simple migration — replace new ScriptTx() with new Tx() and set the fee payer

New Methods on Tx

Script Input Collection

// Collect from script UTXOs with redeemer and optional datum
tx.collectFrom(utxo, redeemer, datum)
tx.collectFrom(utxoList, redeemer, datum)
tx.collectFrom(utxo, redeemer)
tx.collectFrom(utxoList, redeemer)

// Predicate-based script UTXO selection
tx.collectFrom(scriptAddress, utxo -> utxo.getAmount().stream().anyMatch(a -> a.getUnit().equals(tokenUnit)), redeemer, datum)

// Filter-based script UTXO selection
tx.collectFrom(scriptAddress, filterSpec, redeemer, datum)

Reference Inputs

// Read reference inputs (no spending)
tx.readFrom(utxo1, utxo2)
tx.readFrom(transactionInput)
tx.readFrom(txHash, outputIndex)

Plutus Minting

// Mint with Plutus script (singular: mintAsset)
tx.mintAsset(plutusScript, asset, redeemer)
tx.mintAsset(plutusScript, assets, redeemer, receiver)
tx.mintAsset(plutusScript, assets, redeemer, receiver, outputDatum)

// Mint via reference script (by policy ID)
tx.mintAsset(policyId, asset, redeemer)
tx.mintAsset(policyId, assets, redeemer, receiver)

Note: Native script minting continues to use mintAssets (plural), while Plutus minting uses mintAsset (singular).

Validator Attachment

tx.attachSpendingValidator(plutusScript)
tx.attachMintValidator(plutusScript)
tx.attachCertificateValidator(plutusScript)
tx.attachRewardValidator(plutusScript)
tx.attachProposingValidator(plutusScript)
tx.attachVotingValidator(plutusScript)

Change Address with Datum

tx.withChangeAddress(address, inlineDatum)
tx.withChangeAddress(address, datumHash)

Script-Protected Stake Operations

// Deregister with redeemer
tx.deregisterStakeAddress(stakeAddr, redeemer)

// Delegate with redeemer
tx.delegateTo(stakeAddr, poolId, redeemer)

// Withdraw with redeemer
tx.withdraw(rewardAddr, amount, redeemer)
tx.withdraw(rewardAddr, amount, redeemer, receiver)

Script-Protected Governance Operations

tx.registerDRep(credential, anchor, redeemer)
tx.unRegisterDRep(credential, refundAddress, refundAmount, redeemer)
tx.updateDRep(credential, anchor, redeemer)
tx.createProposal(govAction, returnAddress, anchor, redeemer)
tx.createVote(voter, govActionId, vote, anchor, redeemer)
tx.delegateVotingPowerTo(address, dRep, redeemer)

Usage Examples

Script Input with Payment

Tx tx = new Tx()
        .collectFrom(scriptUtxo, redeemer)
        .attachSpendingValidator(spendingScript)
        .payToAddress(receiver, Amount.ada(10))
        .from(senderAddress);

TxResult result = quickTxBuilder.compose(tx)
        .withSigner(SignerProviders.signerFrom(sender))
        .completeAndWait();

Reference Inputs

Tx tx = new Tx()
        .collectFrom(scriptUtxo, redeemer)
        .readFrom(referenceUtxo)           // Reference input for inline datum/script
        .payToAddress(receiver, Amount.ada(5))
        .from(senderAddress);

Plutus Minting

Asset token = Asset.builder()
        .name("MyPlutusToken")
        .value(BigInteger.valueOf(100))
        .build();

Tx tx = new Tx()
        .mintAsset(mintingScript, token, PlutusData.unit(), receiverAddress)
        .from(senderAddress);

TxResult result = quickTxBuilder.compose(tx)
        .withSigner(SignerProviders.signerFrom(sender))
        .completeAndWait();

Mixed Operations in One Transaction

// Combine native payment, Plutus minting, and script input in a single Tx
Tx tx = new Tx()
        .payToAddress(receiver1, Amount.ada(5))              // Native payment
        .mintAsset(mintScript, token, PlutusData.unit())     // Plutus minting
        .collectFrom(scriptUtxo, spendRedeemer)              // Script input
        .attachSpendingValidator(spendingScript)
        .from(senderAddress);

Migration Guide

Replace new ScriptTx() with new Tx(). Calls with a redeemer keep the same names and arguments. Calls to collectFrom without a redeemer are different: Tx has no collectFrom(Utxo), and Tx.collectFrom(List<Utxo>) adds regular inputs rather than script inputs, so pass a redeemer when you spend from a script.

Before (0.7.x)

ScriptTx scriptTx = new ScriptTx()
        .collectFrom(scriptUtxo, redeemer, datum)
        .payToAddress(receiver, Amount.ada(10))
        .attachSpendingValidator(validator);

quickTxBuilder.compose(scriptTx)
        .feePayer(senderAddress)
        .withSigner(SignerProviders.signerFrom(sender))
        .completeAndWait();

After (0.8.0)

Tx tx = new Tx()
        .collectFrom(scriptUtxo, redeemer, datum)
        .payToAddress(receiver, Amount.ada(10))
        .attachSpendingValidator(validator)
        .from(senderAddress);

quickTxBuilder.compose(tx)
        .withSigner(SignerProviders.signerFrom(sender))
        .completeAndWait();

.from(senderAddress) sets the sender, who also pays the fee. You can also keep .feePayer(senderAddress) on the builder, which still works for a script transaction.

How Detection Works

You don’t need to configure anything. When QuickTxBuilder processes a Tx, it automatically detects whether the transaction involves scripts by checking hasScriptIntents() — a data-driven inspection of the transaction’s intentions list. If any script-related intents are present (script inputs, Plutus minting, or any operation with a redeemer), the builder applies script-specific processing (collateral selection, execution unit evaluation, etc.) automatically.

Comparison

Aspect	Before (0.7.x)	After (0.8.0)
Class choice	Tx for regular, ScriptTx for scripts	Tx for everything
Script inputs	ScriptTx.collectFrom(utxo, redeemer)	Tx.collectFrom(utxo, redeemer)
Plutus minting	ScriptTx.mintAsset(script, asset, redeemer)	Tx.mintAsset(script, asset, redeemer)
Validator attachment	ScriptTx.attachSpendingValidator(script)	Tx.attachSpendingValidator(script)
Mixing operations	Compose separate Tx + ScriptTx	Single Tx with all operations
Backward compatibility	N/A	ScriptTx still works (deprecated)