Apollo v2

Pure Go building blocks for constructing Cardano transactions.

Apollo uses the Blink Labs ledger packages for Cardano types, CBOR, scripts, addresses, and transaction bodies.

Install

Apollo v2 requires Go 1.25.13 or newer — the go directive in go.mod is a hard floor, so an older 1.25 patch release fails to build:

go get github.com/Salvionied/apollo/v2

See the documentation index, the v1-to-v2 migration guide, and the SundaeSwap fork migration notes.

Sample usage

package main

import (
    "encoding/hex"
    "fmt"

    "github.com/blinklabs-io/gouroboros/ledger/common"

    apollo "github.com/Salvionied/apollo/v2"
    "github.com/Salvionied/apollo/v2/backend/blockfrost"
)

func main() {
    bfc := blockfrost.NewBlockFrostChainContext(
        "https://cardano-mainnet.blockfrost.io/api/v0",
        1,
        "your_blockfrost_project_id",
    )

    mnemonic := "your mnemonic here"
    a := apollo.New(bfc)
    var err error
    a, err = a.SetWalletFromMnemonic(mnemonic)
    if err != nil {
        panic(err)
    }

    utxos, err := bfc.Utxos(a.GetWallet().Address())
    if err != nil {
        panic(err)
    }

    receiver, err := common.NewAddress("addr1...")
    if err != nil {
        panic(err)
    }

    a, err = a.AddLoadedUTxOs(utxos...).
        PayToAddress(receiver, 1_000_000).
        Complete()
    if err != nil {
        panic(err)
    }

    a, err = a.Sign()
    if err != nil {
        panic(err)
    }

    txCbor, err := a.GetTxCbor()
    if err != nil {
        panic(err)
    }
    fmt.Println(hex.EncodeToString(txCbor))

    txId, err := a.Submit()
    if err != nil {
        panic(err)
    }
    fmt.Println(hex.EncodeToString(txId.Bytes()))
}

Coin Selection

Apollo selects transaction inputs with MACS (Multi-Asset Coin Selection, IEEE Blockchain 2023) by default. MACS prioritizes UTxOs by value and closeness to the pool's average, covering each asset in the target directly. Compared to the legacy largest-first strategy it selects far fewer inputs on multi-asset targets (15 vs 785 in our 1k-UTxO benchmark), produces much smaller change, and sweeps dust UTxOs so they don't accumulate in your wallet.

The algorithm is pluggable via the CoinSelector interface:

// Default: MACS with dust sweeping (UTxOs under 1 ADA, max 2 per tx)
a := apollo.New(bfc)

// Legacy largest-first behavior
a = a.SetCoinSelector(&apollo.LargestFirstSelector{})

// MACS without dust sweeping, or with custom limits
a = a.SetCoinSelector(&apollo.MACSSelector{})
a = a.SetCoinSelector(&apollo.MACSSelector{DustThreshold: 2_000_000, MaxDustInputs: 4})

Benchmarks live in coinselection_bench_test.go (go test -bench BenchmarkCoinSelection), and the design notes with full results are in docs/design/2026-06-11-macs-coin-selection-design.md.

Evaluation witnesses

When a script transaction has required signers, Apollo supplies valid, evaluation-only witnesses to the execution-unit evaluator. BursaWallet provides its payment and stake witnesses automatically. Watch-only, hardware, and remote wallets can provide the required signatures without changing the Wallet interface:

type remoteEvaluationSigner struct{}

func (remoteEvaluationSigner) EvaluationWitnesses(
    bodyHash common.Blake2b256,
    required []common.Blake2b224,
) ([]common.VkeyWitness, error) {
    // Return valid witnesses for any requested hashes controlled remotely.
    return nil, nil
}

a.AddEvaluationWitnessProvider(remoteEvaluationSigner{})

These signatures are used only for EvaluateTx; they are not retained in the final unsigned transaction.

For questions and requests, join the Apollo Discord.

Created by Edoardo Salvioni (Zhaata).