> ## Documentation Index > Fetch the complete documentation index at: https://second.tech/docs/llms.txt > Use this file to discover all available pages before exploring further. # 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. ## OpenAPI ````yaml https://gitlab.com/ark-bitcoin/bark/-/raw/master/bark-rest/openapi.json post /api/v1/exits/presign openapi: 3.1.0 info: title: barkd REST API description: >- A simple REST API for barkd, a wallet daemon for integrating bitcoin payments into your app over HTTP. Supports self-custodial Lightning, Ark, and on-chain out of the box. barkd is a long-running daemon best suited for always-on or high-connectivity environments like nodes, servers, desktops, and point-of-sale terminals. All endpoints return JSON. Amounts are denominated in satoshis. contact: name: Second Team email: hello@second.tech license: name: MIT identifier: MIT version: 0.8.1 servers: [] security: - bearer: [] tags: - name: boards description: Move on-chain bitcoin onto the Ark protocol. - name: exits description: Move bitcoin back on-chain without server cooperation. - name: fees description: Estimate fees for wallet operations before executing them. - name: history description: Inspect and annotate wallet movement history. - name: lightning description: Create Lightning invoices and track receives. - name: message description: Sign arbitrary messages with the wallet's keys and verify signed messages. - name: onchain description: Manage barkd's on-chain bitcoin wallet. - name: wallet description: Manage Ark balances and VTXOs, send payments via Ark, LN, and on-chain. - name: bitcoin description: Query bitcoin network data. - name: notifications description: Receive real-time notifications from barkd. paths: /api/v1/exits/presign: post: tags: - exits summary: Presign emergency exit chains description: >- 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. operationId: exit_presign requestBody: content: application/json: schema: $ref: '#/components/schemas/ExitPresignRequest' required: true responses: '200': description: Returns the presigned exit packages content: application/json: schema: $ref: '#/components/schemas/PresignedExits' '400': description: >- A VTXO is unknown, non-standard, already exited, or already spent, or a parameter is invalid content: application/json: schema: $ref: '#/components/schemas/BadRequestError' '500': description: Internal server error content: application/json: schema: $ref: '#/components/schemas/InternalServerError' components: schemas: ExitPresignRequest: type: object description: Request body for presigning emergency exit chains. properties: fee_rate_sat_per_vb: type: - number - 'null' format: double description: >- The fee rate to sign the CPFP children at, in sat/vB (fractions allowed). When omitted, the current `fast` rate is used. vtxos: type: - array - 'null' items: type: string description: >- 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. PresignedExits: type: object description: >- 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. required: - exits - waves properties: exits: type: array items: $ref: '#/components/schemas/PresignedExit' description: One entry per requested VTXO, in request order. waves: type: array items: $ref: '#/components/schemas/PresignedWave' description: >- 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. BadRequestError: type: object required: - message properties: message: type: string InternalServerError: type: object required: - message properties: message: type: string PresignedExit: type: object description: The presigned broadcast work for one VTXO. required: - vtxo_id - status - unsigned properties: status: $ref: '#/components/schemas/PresignedExitStatus' unsigned: type: array items: $ref: '#/components/schemas/TransactionInfo' description: >- The remaining tail of this exit's chain that could not be funded, in broadcast order; its first transaction spends this exit's last signed one. Empty when fully signed. vtxo_id: type: string PresignedWave: type: object description: One step of the broadcast plan; see [PresignedExits] for the rules. required: - packages - in_mempool properties: in_mempool: type: array items: $ref: '#/components/schemas/TransactionInfo' description: >- Exit transactions already in the mempool; they confirm with this wave. Only the first wave has any. packages: type: array items: $ref: '#/components/schemas/PresignedExitPackage' description: Packages funded independently of each other, broadcast together. PresignedExitStatus: oneOf: - type: object description: >- Every package has a signed child; the exit's broadcast completes once wave `exited_in_wave` confirms (absent when the chain is already confirmed and there is nothing to broadcast). `fee_info` totals the children's fees over the combined weight of this exit's packages. required: - fee_info - type properties: exited_in_wave: type: - integer - 'null' minimum: 0 fee_info: $ref: '#/components/schemas/FeeInfo' type: type: string enum: - fully-signed - type: object description: >- Confirmed funds ran out mid-chain: wave `last_wave` holds this exit's last signed package and `unsigned` continues right after it. required: - last_wave - type properties: last_wave: type: integer minimum: 0 type: type: string enum: - partially-signed - type: object description: No package could be funded. required: - type properties: type: type: string enum: - unsigned description: >- How much of a [PresignedExit]'s remaining broadcast work could be funded and signed. TransactionInfo: type: object description: >- An information struct used to pair the ID of a transaction with the full transaction for ease of use and readability for the user required: - txid - tx properties: tx: type: string txid: type: string PresignedExitPackage: type: object description: An `(exit, child)` transaction package, to be broadcast as one unit. required: - vtxo_id - exit - child properties: child: $ref: '#/components/schemas/PresignedExitChildInfo' description: The signed CPFP child paying for `exit`. exit: $ref: '#/components/schemas/TransactionInfo' description: The zero-fee exit transaction. vtxo_id: type: string description: The VTXO whose exit this package advances. FeeInfo: type: object description: >- Contains the data required to bump the fee for a given transaction (including ancestors). required: - fee_rate_sat_per_kvb - total_fee_sat properties: fee_rate_sat_per_kvb: type: integer format: int64 description: >- The effective fee rate of the transaction (including unconfirmed CPFP ancestors), in sats per kvB. `kvb` matches the unit used elsewhere in `bark-json` (e.g. `offboard_feerate_sat_per_kvb`). minimum: 0 total_fee_sat: type: integer format: int64 description: >- Sum of the transaction's own fee plus the fee of each of its unconfirmed ancestors. minimum: 0 PresignedExitChildInfo: type: object description: A signed CPFP child transaction and the fee it commits. required: - txid - tx - fee_info properties: fee_info: $ref: '#/components/schemas/FeeInfo' description: >- The exit transaction is zero-fee, so this is the fee of the whole package. tx: type: string txid: type: string securitySchemes: bearer: type: http scheme: bearer bearerFormat: AuthToken description: Base64url-encoded auth token ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.