Opening Orders
Market Order
Executes immediately at the current ask (longs) or bid (shorts).- Trigger: Immediate on submission.
- Execution: Bid/ask price.
- Oracle fee: $0.10 at open.
Limit Order
Waits for the actual trade price (bid or ask) to reach your specified level, then executes at that price or better.- Trigger: Bid/ask crossing your limit price.
- Execution: At the limit price or better.
- Oracle fee: $0.10 at placement. Canceling costs an additional $0.10.
Stop Order
Waits for the mid-price to cross your stop level, then executes immediately as a market order.- Trigger: Mid-price crossing your stop price.
- Execution: Bid/ask price (market execution after trigger).
- Oracle fee: $0.10 at placement. Canceling costs an additional $0.10.
Closing Orders
Close Market
Exits your position immediately at the current bid (longs) or ask (shorts).- Trigger: Immediate on submission.
- Execution: Bid/ask price.
- Oracle fee: Refunded on a successful full close. $0.10 charged on partial closes.
Take-Profit (TP)
Closes your position automatically when price reaches your target in the profitable direction.- Trigger: Bid/ask crossing your TP price.
- Execution: At the TP price (limit-style close).
- Oracle fee: Not charged on automated execution.
Stop-Loss (SL)
Closes your position automatically when price moves against you past a specified level.- Trigger: Mid-price crossing your SL price.
- Execution: Bid/ask price (market-style close).
- Oracle fee: Not charged on automated execution.
Liquidation
Automatically closes your position when collateral falls below the liquidation threshold. Not user-initiated.- Trigger: Mid-price crossing the calculated liquidation price.
- Execution: Bid/ask price, executed by keeper bots (Gelato Functions).
- Cost: Protocol pays gas. Remaining collateral is retained by the protocol as part of settlement.
Bid, Ask, and Mid-Price
Three prices matter on Ostium:- Bid: the price at which you can sell (close a long or open a short).
- Ask: the price at which you can buy (open a long or close a short). Always slightly higher than the bid.
- Mid-price: the midpoint between bid and ask. Used as a reference for triggering stops, stop-losses, and liquidations, but you never actually execute at mid-price.
Execution Model
All pairs currently use bid/ask execution: longs open at the ask and close at the bid; shorts open at the bid and close at the ask. The spread between bid and ask reflects underlying market liquidity.Dynamic spreads are enabled for all crypto and stock pairs. On these pairs, orders execute at a Price-After-Impact that adjusts based on short-term order flow imbalance: zero spread under balanced conditions, wider spread when flow is one-sided. All other pairs use standard bid/ask execution. See Markets for details.
Summary Table
| Order Type | Side | Trigger | Execution | Cancel Cost |
|---|---|---|---|---|
| Market | Open | Immediate | Bid/ask | N/A |
| Limit | Open | Bid/ask crosses limit | At limit or better | $0.10 |
| Stop | Open | Mid-price crosses stop | Bid/ask (market) | $0.10 |
| Close Market | Close | Immediate | Bid/ask | N/A |
| Take-Profit | Close | Bid/ask crosses TP | At TP (limit) | Free |
| Stop-Loss | Close | Mid-price crosses SL | Bid/ask (market) | Free |
| Liquidation | Close | Mid-price crosses liq. price | Bid/ask (limit) | N/A |
FAQ
What's the difference between a Stop and a Stop-Loss?
What's the difference between a Stop and a Stop-Loss?
A Stop (Open Stop) triggers entry into a new position when mid-price crosses a level, then executes as a market order. A Stop-Loss closes an existing position when mid-price hits your stop level, also as a market order. Both trigger on mid-price, but one opens and one closes.
Can I have a TP and SL on the same position?
Can I have a TP and SL on the same position?
Yes. You can set one TP and one SL on a single position simultaneously. Whichever triggers first closes the position and cancels the other. You can also have pending Open Limit or Open Stop orders while other positions are open.
Why did my limit order not fill even though the mid-price reached my level?
Why did my limit order not fill even though the mid-price reached my level?
Limit orders trigger on the actual bid/ask price, not the mid-price. The mid-price may touch your level while the bid or ask remains above (for long limits) or below (for short limits). The order fills only when the execution price reaches your limit or better.
What to Read Next
- Opening a Trade — Step-by-step from market selection to order submission.
- Managing Positions — Adjust TP/SL and collateral on open positions.
- Fees — Oracle fees, opening fees, and all other costs.