Reference

Trading units and rounding

Every Trading quantity is an integer in an atomic unit, and swap rounding always favors existing liquidity providers.

Units

ETH and collateral outputs use attoETH (10⁻¹⁸ ETH).
Shares and LP tokens use attoShares, the 18-decimal atomic uint256 unit: one displayed share is 10¹⁸ attoShares. At an empty SecurityPool, one attoETH creates 10¹⁸ attoShares (one displayed share) of every outcome. Protocol retention makes the later collateral-to-share ratio dynamic, so clients must use the current mutation result rather than assuming this initial rate.
Fees, slippage, initial conditional price, and displayed conditional price use basis points over 10,000 where applicable.
Deadlines and question end times are Unix seconds.
Universe IDs are uint248. A token ID is (universeId << 8) | outcome, with local outcomes INVALID = 0, YES = 1, NO = 2.

Rounding

Exact input computes net = ⌊gross × (10,000 − fee) / 10,000⌋ and out = ⌊reserveOut × net / (reserveIn + net)⌋. Exact output computes net = ⌈reserveIn × out / (reserveOut − out)⌉ and gross = ⌈net × 10,000 / (10,000 − fee)⌉. These directions favor existing LPs.

Liquidity deposits round reserve use down. Removal rounds each reserve output down. Initial alternative odds round the smaller deposited reserve down. Conditional YES is NO / (YES + NO); Conditional NO is YES / (YES + NO).