@hydra-sdk/transaction

TxBuilder — a fluent Cardano transaction builder covering multi-asset transfers, minting and burning, Plutus scripts, staking and Hydra L2.

🎮 Try it first

The Transaction Builder playground is this package with a UI on top: pick inputs, add outputs, mint, attach scripts and datums, then read the generated TypeScript next to the built CBOR. Every builder method below has a control there, so it doubles as a live reference.

🚀 Quick Start

pnpm add @hydra-sdk/transaction @hydra-sdk/cardano-wasm

import { TxBuilder } from '@hydra-sdk/transaction'

const cbor = await new TxBuilder()
  .setInputs(utxos)
  .txOut('addr_test1...', [{ unit: 'lovelace', quantity: '2000000' }])
  .changeAddress(changeAddress)
  .completeCbor()

const signedTx = await wallet.signTx(cbor)
const txHash = await wallet.submitTx(signedTx)

For a Hydra head, pass isHydra: true (and the head's protocol parameters) to the constructor:

const builder = new TxBuilder({ isHydra: true, params: await bridge.getProtocolParameters() })

🧠 WASM memory — the one thing to get right

Every object the builder touches lives in WASM linear memory and is only reclaimed by .free(). The JS garbage collector will not do it promptly, so a build loop leaks unless you help it.

| You need | Use | Who frees | | --- | --- | --- | | Just the CBOR | completeCbor() | The builder — nothing to free | | A live Transaction | complete() | You — call tx.free() when done | | Done with the builder | dispose(), or using builder = new TxBuilder() | The builder frees everything it holds |

For high-volume workloads, reuse one builder with reset() between transactions and dispose() it at the end. See Performance for measurements.

✨ What it builds

• Inputs — setInputs() with four coin-selection strategies, or explicit txIn()
• Outputs — txOut() / addOutput(), multi-asset, inline datums
• Mint & burn — mint(), mintingScript(), mintRedeemerValue()
• Plutus V1/V2/V3 — script inputs, datum hashes, inline datums, redeemers, collateral, reference inputs
• Staking — registerStake(), deregisterStake(), delegateStake(), withdrawal()
• Metadata & validity — metadataValue(), invalidBefore(), invalidAfter()
• Fees — computed from protocol parameters, or pinned with setFee() / setMinFee()
• Script budgets — pass an evaluator and complete() rebuilds with real exUnits so the fee is accurate (omit it for Hydra, which has no on-chain evaluation)

📚 Documentation

• API reference · Building transactions guide
• Mint and burn tokens · Configuration
• Changelog

License

Apache 2.0. Repo | Issues