Bitcoin Settlement

All Bound trades execute and settle on Bitcoin mainnet - not a sidechain, not a rollup.

PSBT-based flow

Every transaction uses PSBTs (Partially Signed Bitcoin Transactions):

1. User requests a quote

2. Bound returns an unsigned PSBT

3. User signs the PSBT with their Trading Wallet key

4. Bound validates the request is still current, then co-signs

5. The fully signed PSBT is broadcast to the Bitcoin network

6. User's balance updates immediately in the Trading Wallet

Trading Wallet

The Trading Wallet is a 2-of-2 Timelocked Multisig:

• User key - held by the user's device (via passkey)

• Bound backend key - held by Bound's signing infrastructure

Both signatures are required for every transaction. This ensures neither party can act unilaterally.

Timelock: Bound's co-signature expires after 3 months. After expiry, users can withdraw funds independently - even if Bound is unavailable. Users are prompted to refresh their Trading Wallet to continue using the platform.

Sequencer flow

User submits BTC raw tx
    ↓
Sequencer 1: validates (sequence number, signature, format, OPCODEs)
    ↓
Peer validation with other sequencers
    ↓
EVM node: executes swap, updates state
    ↓
Bitcoin signature collected
    ↓
Transaction broadcast to Bitcoin network