Sync Cosign

Sync & Cosign

Coordinate wallet state across devices and run cosigner-validated token flows using @1sat/actions.

This skill covers two related areas:

• Sync actions pull external value into the wallet: payments to derived deposit addresses, message-box payments, and cosign-wrapped token deliveries.
• Cosign covers BAP attestation plus the cosigner-backend helpers that build and finalize cosigner-signed BSV21 transfers.

Calling Pattern

import { createContext, syncAddresses } from '@1sat/actions'

// wallet is positional; options (including services) second
const ctx = createContext(wallet, { services })
const result = await syncAddresses.execute(ctx, {})

Every sync action sets requiresServices: true — services must be present in the context.

Sync Actions

syncAddresses

Derives BRC-29 deposit addresses (default prefix "1sat"), streams new outputs from the 1sat-stack indexer, classifies them, and internalizes them. Tracks a reorg-safe score in a per-identity store (IndexedDB in browsers, bun:sqlite in Node/Bun) so repeat calls only process new outputs. After internalizing, it rotates plain-BSV inbounds into a fresh BRC-29 funding output via sweepDeposit.

Use this on wallet mount or on a schedule to pick up payments sent to the wallet's deposit addresses from any device.

import { createContext, syncAddresses } from '@1sat/actions'

const ctx = createContext(wallet, { services })
const result = await syncAddresses.execute(ctx, {
  prefix: '1sat',   // optional, defaults to '1sat'
  startIndex: 0,    // optional, default 0
  count: 1,         // optional, default 1
  onProgress: (p) => console.log(p),  // optional UI callback
})

console.log(`processed ${result.processed}, failed ${result.failed}`)

// Input: SyncAddressesInput
interface SyncAddressesInput {
  prefix?: string       // keyID prefix, default 'DEFAULT_DEPOSIT_PREFIX' ("1sat")
  startIndex?: number   // first address index, default 0
  count?: number        // number of addresses, default 1
  onProgress?: (progress: SyncProgress) => void
}

// Result: SyncAddressesResult
interface SyncAddressesResult {
  processed: number     // txs internalized
  failed: number        // txs that failed to internalize
  lastScore: number     // reorg-safe score; pass as fromScore next call
  addresses: string[]   // addresses synced
}

syncMessages

Polls a message box (default "payment_inbox") at ${services.baseUrl}/1sat/messagebox using AuthFetch, internalizes each BRC-29 paymail payment, and acknowledges only the messages that internalized successfully.

import { createContext, syncMessages } from '@1sat/actions'

const ctx = createContext(wallet, { services })
const result = await syncMessages.execute(ctx, {
  messageBox: 'payment_inbox',  // optional, this is the default
})

console.log(`processed ${result.processed}, failed ${result.failed}`)

// Input: SyncMessagesInput
interface SyncMessagesInput {
  messageBox?: string   // default 'payment_inbox'
}

// Result: SyncMessagesResult
interface SyncMessagesResult {
  processed: number
  failed: number
}

syncCosignDeliveries

One-shot pull from a MessageBox slot (default "cosign_token_inbox", server default https://messagebox.1sat.app) used by cosign-wrapped BSV21 mints and transfers. Bodies are BRC-2 ECDH/AES-256-GCM ciphertext; this action unwraps and decrypts them with the wallet, then internalizes the owned output into the bsv21 basket with the supplied customInstructions verbatim. When services is present it enriches tags with token symbol/icon/decimals from the BSV21 overlay.

import { createContext, syncCosignDeliveries } from '@1sat/actions'

const ctx = createContext(wallet, { services })
const result = await syncCosignDeliveries.execute(ctx, {
  messageBox: 'cosign_token_inbox',         // optional default
  messageboxUrl: 'https://messagebox.1sat.app',  // optional default
})

console.log(`processed ${result.processed}, failed ${result.failed}`)

// Input: SyncCosignDeliveriesInput
interface SyncCosignDeliveriesInput {
  messageBox?: string     // default 'cosign_token_inbox'
  messageboxUrl?: string  // default 'https://messagebox.1sat.app'
}

// Result: SyncCosignDeliveriesResult
interface SyncCosignDeliveriesResult {
  processed: number
  failed: number
}

Attest

attest is an Action (publishes a transaction), so it uses the same createContext / .execute pattern. It publishes a BAP ATTEST OP_RETURN (BAP_PREFIX | "ATTEST" | attestationHash | counter) signed with AIP via the current signing key. The output lands in the bap basket. Requires that an identity has already been published (see ../identity/SKILL.md).

import { createContext, attest } from '@1sat/actions'

const ctx = createContext(wallet, { services })
const result = await attest.execute(ctx, {
  attestationHash: '<sha256 of urn:bap:id:attribute:value:nonce>',
  counter: '0',   // optional, default '0'
})

if (result.error) {
  // e.g. 'no-identity: publish identity first'
} else {
  console.log('Attested. txid:', result.txid)
}

// Input: AttestRequest
interface AttestRequest extends ActionOptions {
  /** SHA-256 hash of the attestation URN */
  attestationHash: string
  /** Attestation sequence number, default '0' */
  counter?: string
}

// Response: IdentityResponse
interface IdentityResponse {
  txid?: string
  tx?: number[]
  bapId?: string
  error?: string
}

The output is tagged type:attest, hash:<attestationHash>.

Cosigner Transfer Helpers

These are plain async functions, not Action objects — they do not take a context or use .execute. Each takes a single input object that carries its own wallet and services. They are intended for a cosigner backend that constructs, validates, and broadcasts cosigner-signed BSV21 transfers.

buildCosignDestination

Derives a cosign-wrapped locking script for a recipient using BRC-42 derivation between the caller's wallet and the recipient, embedding the cosigner's identity key as second signer. This one takes a context (it derives via ctx.wallet).

import { createContext, buildCosignDestination } from '@1sat/actions'

const ctx = createContext(wallet, { services })
const { lockingScript, address } = await buildCosignDestination(ctx, {
  recipientIdentityKey: '<recipient identity pubkey hex>',
  cosignerIdentityKey: '<cosigner identity pubkey hex>',
  keyID: '<brc-42 derivation keyID>',
})

// Input: BuildCosignDestinationInput
interface BuildCosignDestinationInput {
  recipientIdentityKey: string
  cosignerIdentityKey: string
  keyID: string
}

// Result: BuildCosignDestinationResult
interface BuildCosignDestinationResult {
  lockingScript: LockingScript
  address: string
}

prepareCosignBsv21Transfer

Phase one of the two-request cosigner flow. The cosigner constructs the unsigned tx (cosign-wrapped transfer outputs, optional multisig holding outputs, optional burns), allocates funding via its own BRC-100 wallet (createAction with signAndProcess: false), persists the session via the supplied CosignSessionStore, and returns the signable BEEF plus per-input sighashes for the sender to sign.

import {
  prepareCosignBsv21Transfer,
  InMemoryCosignSessionStore,
} from '@1sat/actions'

const sessionStore = new InMemoryCosignSessionStore()
const prepared = await prepareCosignBsv21Transfer({
  wallet: cosignerWallet,        // WalletInterface (cosigner's BRC-100 wallet)
  services,                      // OneSatServices
  tokenId,
  tokenInputs: [{ outpoint }],
  inputBEEF,                     // number[] atomic BEEF of inputs
  destinations: [{ recipientIdentityKey, amount }],
  senderIdentityKey,
  sessionStore,
})
// prepared: { sessionId, signableBeef, reference, sighashes }

// Input: PrepareCosignBsv21TransferInput (selected fields)
interface PrepareCosignBsv21TransferInput {
  wallet: WalletInterface
  services: OneSatServices
  tokenId: string
  tokenInputs: CosignTokenInput[]          // { outpoint: 'txid.vout' }
  inputBEEF: number[]
  destinations: CosignTransferDestination[] // { recipientIdentityKey, amount }
  multisigDestinations?: CosignTransferMultisigDestination[]
  burns?: CosignTransferBurn[]              // { amount }
  senderIdentityKey: string
  sessionStore: CosignSessionStore
}

// Result: PrepareCosignBsv21TransferResult
interface PrepareCosignBsv21TransferResult {
  sessionId: string
  signableBeef: number[]
  reference: string
  sighashes: Array<{ inputIndex: number; sighashHex: string }>
}

Sighashes use SIGHASH_ALL | SIGHASH_FORKID (0x41). The sender's wallet signs the single-SHA256 of each sighash.

finalizeCosignBsv21Transfer

Phase two. The sender returns owner-side signatures; the cosigner adds its own signature per cosign-wrapped input, calls signAction to broadcast, submits the resulting BEEF to the BSV21 overlay, and returns per-recipient delivery payloads for messagebox dispatch.

import { finalizeCosignBsv21Transfer } from '@1sat/actions'

const finalized = await finalizeCosignBsv21Transfer({
  wallet: cosignerWallet,
  services,
  sessionId: prepared.sessionId,
  ownerSigs: [
    { inputIndex: 0, sigHex: '<der sig hex>', ownerPubkeyHex: '<pubkey hex>' },
  ],
  sessionStore,
})
// finalized: { txid, beef, overlayStatus, recipients }

// Input: FinalizeCosignBsv21TransferInput
interface FinalizeCosignBsv21TransferInput {
  wallet: WalletInterface
  services: OneSatServices
  sessionId: string
  ownerSigs: CosignOwnerSig[]   // { inputIndex, sigHex, ownerPubkeyHex }
  sessionStore: CosignSessionStore
}

// Result: FinalizeCosignBsv21TransferResult
interface FinalizeCosignBsv21TransferResult {
  txid: string
  beef: number[]
  overlayStatus: string
  recipients: CosignRecipientPayload[]  // { identityKey, vout, amount, customInstructions }
}

Recipients consume their customInstructions via syncCosignDeliveries (above), which internalizes the delivered output into the bsv21 basket.

Session Store

prepare/finalize share state through a CosignSessionStore:

interface CosignSessionStore {
  save(session: CosignTransferSession): Promise<void>
  load(sessionId: string): Promise<CosignTransferSession | null>
  delete(sessionId: string): Promise<void>
}

InMemoryCosignSessionStore is the default for tests and ephemeral demos. Supply a persistent implementation (e.g. Postgres-backed) for a real backend.

The two-phase signing mechanics (signable BEEF rebuild, script verification, signAction, abort on failure) are covered in ../action-patterns/SKILL.md.

Requirements

bun add @1sat/actions @1sat/wallet @1sat/client @bsv/sdk

Sync actions require services in the context. syncCosignDeliveries and the cosign transfer helpers additionally use @bsv/p2p MessageBox and the BSV21 overlay via services.