exits

Presign emergency exit chains

Signs, without broadcasting, the CPFP child of every transaction that still needs to be broadcast to unilaterally (emergency) exit the specified VTXOs, for as long as the wallet’s confirmed on-chain funds last. The result is a self-contained broadcast plan meant for later execution by any independent party: broadcast all of a wave’s (exit, child) packages together, wait for every one to confirm, then move to the next wave—each wave’s children spend change confirmed by the previous wave. Exit transactions already in the mempool are listed in the first wave’s in_mempool. Each exit’s status reports whether its packages are fully-signed (exited_in_wave names the wave whose confirmation completes the exit), partially-signed (confirmed funds ran out mid-chain; last_wave holds the last signed package and the unfunded tail is listed under unsigned), or unsigned. How much more funding a partial result would need is not reported: adding funds changes which coins the next child selects and therefore what it costs. Use GET /exits/fee for the remaining broadcast cost. Presigning reserves no funds, so a later spend from the on-chain wallet can invalidate the remaining children. It does reveal the on-chain addresses the children pay their change to, so one wallet sync recognizes the whole chain once broadcast, and repeat calls against unchanged funds re-derive the same addresses.

POST

api

exits

presign

Presign emergency exit chains

curl --request POST \
  --url https://api.example.com/api/v1/exits/presign \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "fee_rate_sat_per_vb": 123,
  "vtxos": [
    "<string>"
  ]
}
'

import requests

url = "https://api.example.com/api/v1/exits/presign"

payload = {
    "fee_rate_sat_per_vb": 123,
    "vtxos": ["<string>"]
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({fee_rate_sat_per_vb: 123, vtxos: ['<string>']})
};

fetch('https://api.example.com/api/v1/exits/presign', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.example.com/api/v1/exits/presign",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'fee_rate_sat_per_vb' => 123,
    'vtxos' => [
        '<string>'
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.example.com/api/v1/exits/presign"

	payload := strings.NewReader("{\n  \"fee_rate_sat_per_vb\": 123,\n  \"vtxos\": [\n    \"<string>\"\n  ]\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://api.example.com/api/v1/exits/presign")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"fee_rate_sat_per_vb\": 123,\n  \"vtxos\": [\n    \"<string>\"\n  ]\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.example.com/api/v1/exits/presign")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"fee_rate_sat_per_vb\": 123,\n  \"vtxos\": [\n    \"<string>\"\n  ]\n}"

response = http.request(request)
puts response.read_body

{
  "exits": [
    {
      "status": {
        "fee_info": {
          "fee_rate_sat_per_kvb": 1,
          "total_fee_sat": 1
        },
        "type": "fully-signed",
        "exited_in_wave": 1
      },
      "unsigned": [
        {
          "tx": "<string>",
          "txid": "<string>"
        }
      ],
      "vtxo_id": "<string>"
    }
  ],
  "waves": [
    {
      "in_mempool": [
        {
          "tx": "<string>",
          "txid": "<string>"
        }
      ],
      "packages": [
        {
          "child": {
            "fee_info": {
              "fee_rate_sat_per_kvb": 1,
              "total_fee_sat": 1
            },
            "tx": "<string>",
            "txid": "<string>"
          },
          "exit": {
            "tx": "<string>",
            "txid": "<string>"
          },
          "vtxo_id": "<string>"
        }
      ]
    }
  ]
}

{
  "message": "<string>"
}

{
  "message": "<string>"
}

Authorizations

Authorization

string

header

required

Base64url-encoded auth token

Body

application/json

Request body for presigning emergency exit chains.

fee_rate_sat_per_vb

number<double> | null

The fee rate to sign the CPFP children at, in sat/vB (fractions allowed). When omitted, the current fast rate is used.

vtxos

string[] | null

The IDs of the VTXOs to presign exit chains for, in the order they will be broadcast. When omitted, every spendable VTXO in the wallet is used.

Response

Returns the presigned exit packages

Presigned emergency-exit chains for a set of VTXOs: a wave-by-wave broadcast plan plus a per-VTXO summary.

Execute the plan in wave order: broadcast all of a wave's packages together, then wait for every one, and its in_mempool transactions, to confirm before the next wave — each wave's children spend change confirmed by the previous wave.

exits

object[]

required

One entry per requested VTXO, in request order.

Show child attributes

waves

object[]

required

The broadcast plan. Confirmed transactions are omitted, relayed ones are listed in in_mempool, and a package shared by several exits appears once, under the first exit that references it.

Show child attributes

⌘I

Presign emergency exit chains

curl --request POST \
  --url https://api.example.com/api/v1/exits/presign \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "fee_rate_sat_per_vb": 123,
  "vtxos": [
    "<string>"
  ]
}
'

import requests

url = "https://api.example.com/api/v1/exits/presign"

payload = {
    "fee_rate_sat_per_vb": 123,
    "vtxos": ["<string>"]
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({fee_rate_sat_per_vb: 123, vtxos: ['<string>']})
};

fetch('https://api.example.com/api/v1/exits/presign', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.example.com/api/v1/exits/presign",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'fee_rate_sat_per_vb' => 123,
    'vtxos' => [
        '<string>'
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.example.com/api/v1/exits/presign"

	payload := strings.NewReader("{\n  \"fee_rate_sat_per_vb\": 123,\n  \"vtxos\": [\n    \"<string>\"\n  ]\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://api.example.com/api/v1/exits/presign")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"fee_rate_sat_per_vb\": 123,\n  \"vtxos\": [\n    \"<string>\"\n  ]\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.example.com/api/v1/exits/presign")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"fee_rate_sat_per_vb\": 123,\n  \"vtxos\": [\n    \"<string>\"\n  ]\n}"

response = http.request(request)
puts response.read_body

{
  "exits": [
    {
      "status": {
        "fee_info": {
          "fee_rate_sat_per_kvb": 1,
          "total_fee_sat": 1
        },
        "type": "fully-signed",
        "exited_in_wave": 1
      },
      "unsigned": [
        {
          "tx": "<string>",
          "txid": "<string>"
        }
      ],
      "vtxo_id": "<string>"
    }
  ],
  "waves": [
    {
      "in_mempool": [
        {
          "tx": "<string>",
          "txid": "<string>"
        }
      ],
      "packages": [
        {
          "child": {
            "fee_info": {
              "fee_rate_sat_per_kvb": 1,
              "total_fee_sat": 1
            },
            "tx": "<string>",
            "txid": "<string>"
          },
          "exit": {
            "tx": "<string>",
            "txid": "<string>"
          },
          "vtxo_id": "<string>"
        }
      ]
    }
  ]
}

{
  "message": "<string>"
}

{
  "message": "<string>"
}

Documentation

Bark SDK

Barkd

Run an Ark server

Presign emergency exit chains

Authorizations

Body

Response