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fix(sdk-coin-ada): rejecting ada outputs below 1 ADA #8283

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fix(sdk-coin-ada): rejecting ada outputs below 1 ADA #8283

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3 changes: 2 additions & 1 deletion modules/sdk-coin-ada/src/ada.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -586,7 +586,8 @@ export class Ada extends BaseCoin {
} catch (e) {
if (
e.message === 'Did not find address with funds to recover.' ||
e.message.startsWith('Insufficient funds to recover')
e.message.startsWith('Insufficient funds to recover') ||
e.message.startsWith('Consolidation amount too small')
) {
lastScanIndex = i;
continue;
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88 changes: 63 additions & 25 deletions modules/sdk-coin-ada/src/lib/transactionBuilder.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ import {
} from '@bitgo/sdk-core';
import { Asset, Transaction, TransactionInput, TransactionOutput, Withdrawal, SponsorshipInfo } from './transaction';
import { KeyPair } from './keyPair';
import util, { MIN_ADA_FOR_ONE_ASSET } from './utils';
import util, { MIN_ADA_FOR_ONE_ASSET, MIN_ADA_TRANSFER } from './utils';
import * as CardanoWasm from '@emurgo/cardano-serialization-lib-nodejs';
import { BigNum } from '@emurgo/cardano-serialization-lib-nodejs';

Expand Down Expand Up @@ -297,8 +297,13 @@ export abstract class TransactionBuilder extends BaseTransactionBuilder {

change = change.checked_sub(minAmountNeededForAssetOutput);
} else {
// Native coin send
// Native coin send — reject if below Cardano's minimum output (BabbageOutputTooSmallUTxO)
const amount = CardanoWasm.BigNum.from_str(receiverAmount);
if (amount.less_than(CardanoWasm.BigNum.from_str(MIN_ADA_TRANSFER))) {
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@abhishekagrawal080 abhishekagrawal080 Mar 12, 2026

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do we need this exception for if change.less_than(CardanoWasm.BigNum.from_str(MIN_ADA_TRANSFER))) as well?

throw new BuildTransactionError(
`Transfer amount too small: minimum is 1 ADA (${MIN_ADA_TRANSFER} lovelace), got ${receiverAmount} lovelace`
);
}
outputs.add(
CardanoWasm.TransactionOutput.new(util.getWalletAddress(receiverAddress), CardanoWasm.Value.new(amount))
);
Expand Down Expand Up @@ -392,7 +397,10 @@ export abstract class TransactionBuilder extends BaseTransactionBuilder {
change = change.checked_sub(minAmountNeededForAssetOutput);
});
}
if (!change.is_zero()) {
// Only create a change output if it meets the Cardano minimum output amount.
// If the change is positive but below 1 ADA, it is absorbed into the transaction fee
// (i.e. the miner receives the dust) rather than creating an unspendable UTXO.
if (!change.is_zero() && !change.less_than(CardanoWasm.BigNum.from_str(MIN_ADA_TRANSFER))) {
const changeOutput = CardanoWasm.TransactionOutput.new(changeAddress, CardanoWasm.Value.new(change));
outputs.add(changeOutput);
}
Expand Down Expand Up @@ -524,6 +532,11 @@ export abstract class TransactionBuilder extends BaseTransactionBuilder {
txOutputAmountBuilder = txOutputAmountBuilder.with_coin_and_asset(amount, multiAsset);
outputs.add(txOutputAmountBuilder.build());
} else {
if (amount.less_than(CardanoWasm.BigNum.from_str(MIN_ADA_TRANSFER))) {
throw new BuildTransactionError(
`Transfer amount too small: minimum is 1 ADA (${MIN_ADA_TRANSFER} lovelace), got ${output.amount} lovelace`
);
}
outputs.add(
CardanoWasm.TransactionOutput.new(util.getWalletAddress(output.address), CardanoWasm.Value.new(amount))
);
Expand Down Expand Up @@ -553,7 +566,7 @@ export abstract class TransactionBuilder extends BaseTransactionBuilder {
// If totalAmountToSend is 0, its consolidation
if (totalAmountToSend.to_str() == '0') {
// support for multi-asset consolidation
if (this._multiAssets !== undefined) {
if (this._multiAssets.length > 0) {
const totalNumberOfAssets = CardanoWasm.BigNum.from_str(this._multiAssets.length.toString());
const minAmountNeededForOneAssetOutput = CardanoWasm.BigNum.from_str(MIN_ADA_FOR_ONE_ASSET);
const minAmountNeededForTotalAssetOutputs =
Expand Down Expand Up @@ -582,23 +595,36 @@ export abstract class TransactionBuilder extends BaseTransactionBuilder {
outputs.add(txOutput);
});

// finally send the remaining ADA in its own output
// Only add the remaining ADA output if it meets the protocol minimum.
// If below 1 ADA, the remainder is absorbed into the fee rather than
// creating an unspendable output (BabbageOutputTooSmallUTxO).
const remainingOutputAmount = change.checked_sub(minAmountNeededForTotalAssetOutputs);
const changeOutput = CardanoWasm.TransactionOutput.new(
changeAddress,
CardanoWasm.Value.new(remainingOutputAmount)
);
outputs.add(changeOutput);
if (!remainingOutputAmount.less_than(CardanoWasm.BigNum.from_str(MIN_ADA_TRANSFER))) {
const changeOutput = CardanoWasm.TransactionOutput.new(
changeAddress,
CardanoWasm.Value.new(remainingOutputAmount)
);
outputs.add(changeOutput);
}
}
} else {
// If there are no tokens to consolidate, you only have 1 output which is ADA alone
// ADA-only consolidation — the entire balance (minus fee) becomes the single output.
// Reject if it would be below the Cardano minimum output to prevent BabbageOutputTooSmallUTxO.
if (change.less_than(CardanoWasm.BigNum.from_str(MIN_ADA_TRANSFER))) {
throw new BuildTransactionError(
`Consolidation amount too small: after fees, only ${change.to_str()} lovelace remains which is below the 1 ADA minimum output required by the Cardano protocol`
);
}
const changeOutput = CardanoWasm.TransactionOutput.new(changeAddress, CardanoWasm.Value.new(change));
outputs.add(changeOutput);
}
} else {
// If this isn't a consolidate request, whatever change that needs to be sent back to the rootaddress is added as a separate output here
const changeOutput = CardanoWasm.TransactionOutput.new(changeAddress, CardanoWasm.Value.new(change));
outputs.add(changeOutput);
// If this isn't a consolidate request, whatever change that needs to be sent back to the rootaddress is added as a separate output here.
// Skip the change output if it would be below the Cardano minimum (1 ADA); dust is absorbed into the fee.
if (!change.less_than(CardanoWasm.BigNum.from_str(MIN_ADA_TRANSFER))) {
const changeOutput = CardanoWasm.TransactionOutput.new(changeAddress, CardanoWasm.Value.new(change));
outputs.add(changeOutput);
}
}
}

Expand Down Expand Up @@ -720,7 +746,7 @@ export abstract class TransactionBuilder extends BaseTransactionBuilder {
// If totalAmountToSend is 0, its consolidation
if (totalAmountToSend.to_str() == '0') {
// support for multi-asset consolidation
if (this._multiAssets !== undefined) {
if (this._multiAssets.length > 0) {
const totalNumberOfAssets = CardanoWasm.BigNum.from_str(this._multiAssets.length.toString());
const minAmountNeededForOneAssetOutput = CardanoWasm.BigNum.from_str('1500000');
const minAmountNeededForTotalAssetOutputs = minAmountNeededForOneAssetOutput.checked_mul(totalNumberOfAssets);
Expand Down Expand Up @@ -748,27 +774,39 @@ export abstract class TransactionBuilder extends BaseTransactionBuilder {
outputs.add(txOutput);
});

// finally send the remaining ADA in its own output
// Only add the remaining ADA output if it meets the Cardano protocol minimum.
// If below 1 ADA, the remainder is absorbed into the fee (BabbageOutputTooSmallUTxO prevention).
const remainingOutputAmount = change.checked_sub(minAmountNeededForTotalAssetOutputs);
const changeOutput = CardanoWasm.TransactionOutput.new(
changeAddress,
CardanoWasm.Value.new(remainingOutputAmount)
);
outputs.add(changeOutput);
if (!remainingOutputAmount.less_than(CardanoWasm.BigNum.from_str(MIN_ADA_TRANSFER))) {
const changeOutput = CardanoWasm.TransactionOutput.new(
changeAddress,
CardanoWasm.Value.new(remainingOutputAmount)
);
outputs.add(changeOutput);
}
} else {
throw new BuildTransactionError(
'Insufficient funds: need a minimum of 1.5 ADA per output to construct token consolidation'
);
}
} else {
// If there are no tokens to consolidate, you only have 1 output which is ADA alone
// ADA-only consolidation — the entire balance (minus fee) becomes the single output.
// Reject if it would be below the Cardano minimum output to prevent BabbageOutputTooSmallUTxO.
if (change.less_than(CardanoWasm.BigNum.from_str(MIN_ADA_TRANSFER))) {
throw new BuildTransactionError(
`Consolidation amount too small: after fees, only ${change.to_str()} lovelace remains which is below the 1 ADA minimum output required by the Cardano protocol`
);
}
const changeOutput = CardanoWasm.TransactionOutput.new(changeAddress, CardanoWasm.Value.new(change));
outputs.add(changeOutput);
}
} else {
// If this isn't a consolidate request, whatever change that needs to be sent back to the rootaddress is added as a separate output here
const changeOutput = CardanoWasm.TransactionOutput.new(changeAddress, CardanoWasm.Value.new(change));
outputs.add(changeOutput);
// If this isn't a consolidate request, whatever change needs to be sent back is added as a separate output.
// Skip if below the Cardano minimum (1 ADA); dust is absorbed into the fee.
if (!change.less_than(CardanoWasm.BigNum.from_str(MIN_ADA_TRANSFER))) {
const changeOutput = CardanoWasm.TransactionOutput.new(changeAddress, CardanoWasm.Value.new(change));
outputs.add(changeOutput);
}
}
}

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2 changes: 2 additions & 0 deletions modules/sdk-coin-ada/src/lib/utils.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,8 @@ import bs58 from 'bs58';
import cbor from 'cbor';

export const MIN_ADA_FOR_ONE_ASSET = '1500000';
// Cardano protocol minimum for any ADA-only output (BabbageOutputTooSmallUTxO is thrown if violated)
export const MIN_ADA_TRANSFER = '1000000';
export const VOTE_ALWAYS_ABSTAIN = 'always-abstain';
export const VOTE_ALWAYS_NO_CONFIDENCE = 'always-no-confidence';

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4 changes: 1 addition & 3 deletions modules/sdk-coin-ada/test/unit/ada.ts
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Expand Up @@ -1002,9 +1002,7 @@ describe('ADA', function () {
walletPassphrase: wrwUser.walletPassphrase,
recoveryDestination: destAddr,
})
.should.rejectedWith(
'Insufficient funds to recover, minimum required is 1 ADA plus fees, got 834455 fees: 165545'
);
.should.rejectedWith(/Consolidation amount too small: after fees, only 834455 lovelace remains/);
sandBox.assert.calledTwice(basecoin.getDataFromNode);
});
});
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72 changes: 72 additions & 0 deletions modules/sdk-coin-ada/test/unit/transactionBuilder.ts
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Expand Up @@ -8,6 +8,78 @@ import { Transaction } from '../../src/lib/transaction';

describe('ADA Transaction Builder', async () => {
const factory = new TransactionBuilderFactory(coins.get('tada'));

describe('Minimum output amount validation (BabbageOutputTooSmallUTxO prevention)', () => {
// Shared test inputs — using the same transaction_id and addresses as the Shelley tests above
const txId = '3677e75c7ba699bfdc6cd57d42f246f86f63aefd76025006ac78313fad2bba21';
const recipientAddress = testData.rawTx.outputAddress1.address;
const changeAddress = testData.rawTx.outputAddress2.address;
const totalInput = 21032023;

it('should reject a transfer output of 999999 lovelace (below 1 ADA minimum)', async () => {
const txBuilder = factory.getTransferBuilder();
txBuilder.input({ transaction_id: txId, transaction_index: 1 });
txBuilder.output({ address: recipientAddress, amount: '999999' });
txBuilder.changeAddress(changeAddress, totalInput.toString());
txBuilder.ttl(800000000);
await txBuilder
.build()
.should.be.rejectedWith(
/Transfer amount too small: minimum is 1 ADA \(1000000 lovelace\), got 999999 lovelace/
);
});

it('should reject a transfer output of 0 lovelace', async () => {
const txBuilder = factory.getTransferBuilder();
txBuilder.input({ transaction_id: txId, transaction_index: 1 });
txBuilder.output({ address: recipientAddress, amount: '0' });
txBuilder.changeAddress(changeAddress, totalInput.toString());
txBuilder.ttl(800000000);
await txBuilder
.build()
.should.be.rejectedWith(/Transfer amount too small: minimum is 1 ADA \(1000000 lovelace\), got 0 lovelace/);
});

it('should allow a transfer output of exactly 1 ADA (1000000 lovelace)', async () => {
const txBuilder = factory.getTransferBuilder();
txBuilder.input({ transaction_id: txId, transaction_index: 1 });
txBuilder.output({ address: recipientAddress, amount: '1000000' });
txBuilder.changeAddress(changeAddress, totalInput.toString());
txBuilder.ttl(800000000);
const tx = (await txBuilder.build()) as Transaction;
tx.type.should.equal(TransactionType.Send);
const txData = tx.toJson();
txData.outputs[0].amount.should.equal('1000000');
});

it('should omit change output when change is below 1 ADA (dust absorbed into fee)', async () => {
// totalInput = 1000000 (recipient) + ~167000 (fee) + ~600 (dust) — change would be ~600 lovelace
// With our fix, no change output should appear; the dust becomes extra fee
const dustInput = 1167600;
const txBuilder = factory.getTransferBuilder();
txBuilder.input({ transaction_id: txId, transaction_index: 1 });
txBuilder.output({ address: recipientAddress, amount: '1000000' });
txBuilder.changeAddress(changeAddress, dustInput.toString());
txBuilder.ttl(800000000);
const tx = (await txBuilder.build()) as Transaction;
const txData = tx.toJson();
// Only 1 output (the recipient), the change dust was absorbed into the fee
txData.outputs.length.should.equal(1);
txData.outputs[0].address.should.equal(recipientAddress);
});

it('should reject ADA-only consolidation when amount after fees is below 1 ADA', async () => {
// totalInput so small that after fee estimation the remaining balance < 1 ADA
const tinyInput = 500000;
const txBuilder = factory.getTransferBuilder();
txBuilder.input({ transaction_id: txId, transaction_index: 1 });
// No output = consolidation mode
txBuilder.changeAddress(changeAddress, tinyInput.toString());
txBuilder.ttl(800000000);
await txBuilder.build().should.be.rejectedWith(/Consolidation amount too small/);
});
});

it('start and build an unsigned transfer tx for byron address', async () => {
const txBuilder = factory.getTransferBuilder();
txBuilder.input({
Expand Down
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