Order types

Every Lull order executes once, at the open. There are two types.

Market on open#

A market-on-open (MOO) order has no limit. It takes part in the cross at whatever P_open turns out to be. If your side of the book is heavy, it can also take liquidity from LP quotes, at P_open plus the LP's spread for a buy, or minus it for a sell.

The market caps LP spreads (200 bps by default). So the average price per share of a MOO buy is at most P_open × (1 + widest revealed spread), and the average price of a MOO sell is at least P_open × (1 − widest revealed spread).

Limit on open#

A limit-on-open (LOO) order carries a "Limit (USD per share)". For a buy it is the most you will pay per share. For a sell it is the least you will accept.

At the cross the limit is compared with P_open exactly, in integers:

• If the limit is not met at P_open, the order does not trade, and its full amount returns to your free balance.
• If it is met at P_open, the order takes part in matching at P_open.
• If it is also met at the worst revealed LP price (P_open plus the widest revealed spread for a buy, minus it for a sell), the order can take LP liquidity as well.

Example, with hypothetical numbers: P_open is $200.00 and the widest revealed LP spread for buyers is 100 bps, so the worst LP price is $202.00.

• A buy limited at $199.99 does not trade.
• A buy limited at $201.00 matches at $200.00 but takes no LP liquidity.
• A buy limited at $202.00 or above can take both.

No fill goes past your limit, apart from rounding of at most 2 raw units of each token. The cross explains why the widest spread, and not the spread that actually clears, sets this line.

Sizing: buys in USDC, sells in AAPLx#

• A buy is sized in USDC. The "Amount" is the most you will spend. The number of shares you receive depends on P_open, which does not exist yet when you seal. Locking a USDC amount is the only way to size a buy safely before the price is known.
• A sell is sized in AAPLx shares. The "Amount" is the most you will sell. When you seal, the app converts the shares to the token's raw units with the current Scaled UI multiplier. See Units.

Minimums#

Each market sets a minimum buy and a minimum sell. By default they are 1 USDC for a buy and 0.001 AAPLx before the Scaled UI multiplier (100,000 raw units) for a sell. The order ticket shows the market's current values. The program checks the minimum when you reveal.

Partial fills and refunds#

A buy may spend less than its amount, and a sell may sell less than its amount:

• If your side is lighter than the other at P_open, your order fills in full at P_open.
• If your side is heavier, the matched volume is shared pro rata among the heavy side's orders. LP quotes then absorb what they can of the rest, cheapest first.
• Whatever does not fill returns to your free balance when the ticket is claimed.

Your fill depends on the size of your order, not on when you revealed it within the window. See The cross for the full rules and a worked example.