UTXO

Sign PSBT

Sign a Partially-Signed Bitcoin Transaction with the user's passkey. Supports selective input signing, sighash flags, and optional broadcast.

utxo.signPsbt signs the inputs your session owns in a PSBT, leaving all other inputs untouched. Optionally broadcasts the fully-signed result.

import { utxo } from '@oviato/connect';

const r = await utxo.signPsbt({
  psbt: '70736274ff01007d...', // PSBT as hex
  broadcast: true,
});

if (r.status === 'success') {
  if (r.type === 'signPsbtBroadcastSuccess') {
    console.log('TxID:', r.data.txid);
  } else if (r.type === 'signPsbtSuccess') {
    console.log('Signed PSBT:', r.data.psbt);
  }
}

Parameters

Field	Type	Notes
`psbt`	`string`	PSBT as hex (not base64). Required.
`signInputs`	`SignPsbtInput[]?`	If omitted, every owned input is signed.
`broadcast`	`boolean?`	If `true`, broadcasts after signing. Default `false`.
`method`	`'popup' \| 'iframe'?`	How the approval UI opens.

`SignPsbtInput`

type SignPsbtInput = {
  index: number;         // Which input to sign (0-based)
  address: string;       // The address that owns that input — used for key derivation
  sighashTypes?: number[]; // Optional SIGHASH flags (default: SIGHASH_ALL)
};

Response shape

Discriminated by whether you asked to broadcast.

type Result =
  | { status: 'success'; type: 'signPsbtSuccess'; data: { psbt: string } }
  | { status: 'error'; message: string };

Use this when a different party (a marketplace, aggregator, second cosigner) will broadcast after you sign.

type Result =
  | { status: 'success'; type: 'signPsbtBroadcastSuccess'; data: { txid: string; explorerUrl?: string } }
  | { status: 'error'; message: string };

Use this for straightforward "sign + send" flows where you built the PSBT yourself.

Common flows

Sign all owned inputs + broadcast

The simplest case. psbt in, txid out.

const r = await utxo.signPsbt({
  psbt: rawPsbtHex,
  broadcast: true,
});

if (r.status === 'success' && r.type === 'signPsbtBroadcastSuccess') {
  window.open(r.data.explorerUrl!, '_blank');
}

Sign without broadcasting

Useful for marketplace flows — you sign your half, the counterparty signs + broadcasts.

const r = await utxo.signPsbt({
  psbt: marketplaceBuiltPsbt,
  broadcast: false,
});

if (r.status === 'success' && r.type === 'signPsbtSuccess') {
  await fetch('/api/marketplace/complete', {
    method: 'POST',
    body: JSON.stringify({ signedPsbt: r.data.psbt }),
  });
}

Sign specific inputs only

If the PSBT has inputs owned by multiple addresses and you want to sign only some:

import { SigHashTypes } from '@oviato/connect';

const r = await utxo.signPsbt({
  psbt: rawPsbtHex,
  signInputs: [
    { index: 0, address: session.address },
    { index: 2, address: session.address, sighashTypes: [SigHashTypes.SINGLE | SigHashTypes.ANYONECANPAY] },
  ],
  broadcast: false,
});

Default sighash is SIGHASH_ALL — signs over all inputs + outputs. Use SIGHASH_SINGLE | SIGHASH_ANYONECANPAY for marketplace flows where your signature covers only your input and its matching output.

Getting a PSBT

PSBTs usually come from one of two places:

Your own backend. You do coin-selection + construct the transaction server-side and pass the PSBT hex to the frontend for signing.
A counterparty or protocol. A different party builds the PSBT and hands it to you to add your signature.

Either way, the PSBT arrives as a hex string that you pass directly to utxo.signPsbt.

Validation before signing

The bridge UI decodes the PSBT before showing the user, flagging:

Which inputs they own (green), which they don't (grey)
Which outputs go to them (change), which go elsewhere
Estimated network fee
Any unusual characteristics (OP_RETURN, large opcodes, etc.)

The user can always see the full decoded tx before approving.

Send Transfers — simpler native BTC sends
Recipes — common UTXO flows

UTXO Overview

Oviato's UTXO surface — PSBT signing for Bitcoin, scoped under utxo.*. Everything else lives at the top level (sendTransfer, signMessage, getBalance).

UTXO Recipes

Common Bitcoin flows — multi-recipient send, balance prechecks, confirmation polling.

Sign PSBT

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