Trading Model

Trading Model

bitCaster uses a central limit order book (CLOB). A limit order can rest on the book. A crossing order takes available liquidity. All product assets are sats.

Public market books use primitive outcome routes. A categorical market exposes A / Not A, B / Not B, and similar books. Clients use the market identifier {conditionId}-{outcomeName} and select the required token side.

Order authorization

A wallet supplies a PAY_TO_UNLOCK capability when it submits an order. The engine validates the capability during order admission. It makes no mint network call during admission.

The capability covers an authorized range. A range continuation requires a new authorization. Cancellation retracts only a resting order. It does not spend a capability and it does not trigger a capability refund.

Fills and settlement groups

Each matched quantity creates one fill. fillId identifies that real fill.

The engine can group one or more fills into one atomic settlement group. groupId identifies the settlement group. The mint receives one multi-party conversion for the group. The current product supports complementary and mint conversion. It does not expose merge conversion in this release.

Mint confirmation returns exact result entries. Clients retain their submitted operations and confirmed results. They can recover those exact records after a crash. If the result is uncertain, clients reconcile with the durable engine and mint authority.

Participation Score

Participation Score protects public order admission and charges durable fills. Each non-exempt participant pays the configured debit for each durable fill. It is not a settlement-negligence penalty. The approved operator wallet service does not receive Score debits.

Trust boundary

The engine receives the exact PAY_TO_UNLOCK proofs that authorize an order. It sees their secrets and the public blinded-output manifest. It does not receive the wallet seed, output blinding factors, refund key, or other wallet proofs.

The engine can use only the authorized selection before expiry. It cannot redirect value outside the manifest or extend the lock. If it withholds settlement, the authorized proofs remain unavailable until refund becomes valid.

The mint performs the conversion. Wallets control their proof material. A PAY_TO_UNLOCK capability can refund after expiry under the NUT rules.

Comparison with on-chain CTF exchanges

The names complementary, mint, and merge also appear in on-chain CTF systems. The implementation differs. bitCaster currently exposes complementary and mint conversion only. It uses one mint conversion for an atomic settlement group. It does not use a peer-to-peer settlement exchange or an on-chain operator transaction.