Timelock

Lock and unlock BSV until specific block heights using @1sat/actions.

Actions

Action	Description
getLockData	Get summary of all locks (total, unlockable, next unlock)
lockBsv	Lock BSV until a specific block height
unlockBsv	Unlock all matured (expired) locks

Check Lock Status

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

const ctx = createContext(wallet, { services })

const data = await getLockData.execute(ctx, {})

console.log(`Total locked: ${data.totalLocked} sats`)
console.log(`Unlockable now: ${data.unlockable} sats`)
console.log(`Next unlock at block: ${data.nextUnlock}`)

LockData Response

interface LockData {
  totalLocked: number   // Total satoshis in all locks
  unlockable: number    // Satoshis that can be unlocked now
  nextUnlock: number    // Block height of next maturing lock
}

Lock BSV

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

const ctx = createContext(wallet, { services })

// Lock 10,000 sats until block 900000
const result = await lockBsv.execute(ctx, {
  requests: [
    { satoshis: 10000, until: 900000 },
  ],
})

// Multiple locks in one transaction
const result = await lockBsv.execute(ctx, {
  requests: [
    { satoshis: 5000, until: 880000 },
    { satoshis: 10000, until: 900000 },
    { satoshis: 50000, until: 950000 },
  ],
})

if (result.txid) {
  console.log('Locked! txid:', result.txid)
}

Unlock Matured Locks

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

const ctx = createContext(wallet, { services })

const result = await unlockBsv.execute(ctx, {})

if (result.txid) {
  console.log('Unlocked! txid:', result.txid)
} else if (result.error === 'no-matured-locks') {
  console.log('No locks ready to unlock yet')
}

How Unlocking Works

1. Lists all outputs in the locks basket
2. Checks each lock's until: tag against current block height
3. Filters to only matured locks (until <= currentHeight)
4. Calls createAction with signAndProcess: false to build the unsigned transaction
5. Calls completeSignedAction which handles BEEF merge, signing, script verification, signAction, and abort on failure
6. The signing callback uses Lock.unlockWithWallet per input

completeSignedAction Pattern

All two-phase unlock operations use the completeSignedAction helper:

import { completeSignedAction } from '@1sat/actions'
import { Lock } from '@1sat/templates'

const result = await completeSignedAction(
  ctx.wallet,
  createResult,
  inputBEEF as number[],
  async (tx) => {
    const spends: Record<number, { unlockingScript: string }> = {}
    for (let i = 0; i < maturedLocks.length; i++) {
      const lock = maturedLocks[i]
      const unlocker = Lock.unlockWithWallet(
        ctx.wallet,
        lock.protocolID,
        lock.keyID,
        'self',
      )
      const unlockingScript = await unlocker.sign(tx, i)
      spends[i] = { unlockingScript: unlockingScript.toHex() }
    }
    return spends
  },
)

The helper handles:

• Merging the signable transaction BEEF with inputBEEF (fixes stripped merkle proofs)
• Calling the signing callback with a fully-wired Transaction
• Verifying unlocking scripts against locking scripts before submitting
• Calling signAction to finalize
• Calling abortAction automatically on failure

How the Lock Script Works

The lock script combines a CLTV (CheckLockTimeVerify) check with a P2PKH signature check:

<lockPrefix> <pubKeyHash> <blockHeight> <lockSuffix>

To unlock:

• Transaction nLockTime must be >= the lock's block height
• Input sequenceNumber must be 0 (enables nLockTime checking)
• Valid signature from the lock key
• Sighash preimage for script verification

Lock Input Parameters

When building createAction inputs for lock outputs:

• unlockingScriptLength: 1205 (accounts for DER signature variability)
• sequenceNumber: 0 (required for nLockTime)
• anyoneCanPay must be false (the default)

Lock Storage

Locks are stored in the locks basket with tags:

Tag	Meaning
until:{height}	Block height when the lock matures

Custom instructions store the protocol and key info for unlocking.

Minimum Unlock Amount

There is a minimum unlock threshold (MIN_UNLOCK_SATS) to prevent dust unlock attempts. If your matured locks total less than this threshold per lock, they won't appear as unlockable.

Current Block Height

The lock module uses services.chaintracks.currentHeight() to determine the current block height. You can also check it directly:

const res = await fetch('https://api.1sat.app/1sat/chaintracks/height')
const height = await res.json()
console.log('Current height:', height)

Requirements

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

Unlock operations require services for current block height lookup.